Merge opl-branch to trunk.

OPL support still isn't perfect, and it certainly isn't complete.
However, for now, it's good enough.

Subversion-branch: /trunk/chocolate-doom
Subversion-revision: 1878

36 files changed, 6823 insertions, 38 deletions

diff --git a/BUGS b/BUGS
index 5dd8a531..ee6bf09a 100644
--- a/BUGS
+++ b/BUGS
@@ -6,21 +6,6 @@
   effects are cut off at the wrong distance. This needs further 
   investigation.
 
-* Music plays back differently.
-
-  Vanilla Doom was typically played with a SoundBlaster (or compatible)
-  card.  It programmed the registers for the OPL music chip directly
-  in order to emulate the various General MIDI instruments.  However,
-  Chocolate Doom uses the OS's native MIDI playback interfaces to play
-  MIDI sound.  As the OPL is programmed differently, the music sounds
-  different to the original, even when using an original SoundBlaster
-  card.
-
-  This can be worked around in the future: OPL emulation code exists that
-  simulates an OPL chip in software.  Furthermore, depending on the OS,
-  it may be possible to program the OPL directly in order to get the 
-  same sound.
-
 * A small number of Doom bugs are almost impossible to emulate.
 
   An example of this can be seen in Ledmeister's "Blackbug" demo which 
diff --git a/Makefile.am b/Makefile.am
index a980acde..13e8bddb 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -42,6 +42,7 @@ EXTRA_DIST=                             \
         config.h                        \
         CMDLINE                         \
         HACKING                         \
+        README.OPL                      \
         TODO                            \
         BUGS                            \
         rpm.spec
@@ -49,7 +50,7 @@ EXTRA_DIST=                             \
 MAINTAINERCLEANFILES =  $(AUX_DIST_GEN)
 
 docdir=$(prefix)/share/doc/@PACKAGE@
-SUBDIRS=wince textscreen pcsound src man setup
+SUBDIRS=wince textscreen opl pcsound src man setup
 DIST_SUBDIRS=pkg $(SUBDIRS)
 
 if HAVE_PYTHON
diff --git a/OPL-TODO b/OPL-TODO
new file mode 100644
index 00000000..6252bc2a
--- /dev/null
+++ b/OPL-TODO
@@ -0,0 +1,20 @@
+
+opl-branch TODO list
+
+Needs research:
+
+ * Strategy when no more voices are available is still wrong
+ * Scale levels don't exactly match Vanilla (off-by-one?)
+
+Bad MIDIs:
+
+ * doom2.wad MAP01
+ * gothicdm MAP05
+ * tnt.wad MAP30
+ * Alien Vendetta (title screen, MAP01, etc)
+
+Other tasks:
+
+ * Get a better software OPL emulator
+ * DMXOPTIONS opl3/phase option support.
+
diff --git a/README.OPL b/README.OPL
new file mode 100644
index 00000000..07699232
--- /dev/null
+++ b/README.OPL
@@ -0,0 +1,107 @@
+== Chocolate Doom hardware OPL support notes ==
+
+Chocolate Doom is able to play MIDI music as it sounds in Vanilla Doom
+with an OPL chip (as found in the Yamaha Adlib card, the Sound Blaster
+and its clones).  Most modern computers do not include an OPL chip any
+more, as CPUs are fast enough to do decent software MIDI synthesis.
+For this reason, a software OPL emulator is included as a substitute.
+
+However, no software emulator sounds exactly like a real (hardware)
+OPL chip, so if you do have a sound card with hardware OPL, here's how
+to configure Chocolate Doom to use it.
+
+=== Sound cards with OPL chips ===
+
+If you have an ISA sound card, it almost certainly includes an OPL
+chip.  Modern computers don't have slots for ISA cards though, so you
+must be running a pretty old machine.
+
+If you have a PCI sound card, you probably don't have an OPL chip.
+However, there are some exceptions to this. The following cards are
+known to include "legacy" OPL support:
+
+    * C-Media CMI8738 (*)
+    * Forte Media FM801
+    * Cards based on the Yamaha YMF724 (*)
+
+Other cards that apparently have OPL support but have not been tested:
+
+    * S3 SonicVibes
+    * AZTech PCI 168 (AZT 3328 chipset)
+    * ESS Solo-1 sound cards (ES1938, ES1946, ES1969 chipset)
+    * Conexant Riptide Audio/Modem combo cards
+    * Cards based on the Crystal Semiconductors CS4281
+    * Cards based on the Avance Logic ALS300
+    * Cards based on the Avance Logic ALS4000
+
+If you desperately want hardware OPL music, you may be able to find
+one of these cards for sale cheap on eBay.
+
+For the cards listed above with (*) next to them, OPL support is
+disabled by default and must be explictly enabled in software.
+
+If your machine is not a PC, you don't have an OPL chip, and you will
+have to use the software OPL.
+
+=== Operating System support ===
+
+If you're certain that you have a sound card with hardware OPL, you
+may need to take extra steps to configure your operating system to
+allow access to it.  To do hardware OPL, Chocolate Doom must access
+the chip directly, which is usually not possible in modern operating
+systems unless you are running as the superuser (root/Administrator).
+
+=== Windows 9x ===
+
+If you're running Windows 95, 98 or Me, there is no need to configure
+anything.  Windows allows direct access to the OPL chip.  You can
+confirm that hardware OPL is working by checking for this message in
+stdout.txt:
+
+    OPL_Init: Using driver 'Win32'.
+
+=== Windows NT (including 2000, XP and later) ===
+
+If you're running an NT-based system, it is not possible to directly
+access the OPL chip, even when running as Administrator.  Fortunately,
+it is possible to use the "ioperm.sys" driver developed for Cygwin:
+
+    http://openwince.sourceforge.net/ioperm/
+
+It is not necessary to have Cygwin installed to use this.  Copy the
+ioperm.sys file into the same directory as the Chocolate Doom
+executable and it should be automatically loaded.
+
+You can confirm that hardware OPL is working by checking for this
+message in stdout.txt:
+
+    OPL_Init: Using driver 'Win32'.
+
+=== Linux ===
+
+If you are using a system based on the Linux kernel, you can access
+the OPL chip directly, but you must be running as root.  You can
+confirm that hardware OPL is working, by checking for this message on
+startup:
+
+    OPL_Init: Using driver 'Linux'.
+
+If you are using one of the PCI cards in the list above with a (*)
+next to it, you may need to manually enable FM legacy support.  Add
+the following to your /etc/modprobe.conf file to do this:
+
+    options snd-ymfpci fm_port=0x388
+    options snd-cmipci fm_port=0x388
+
+=== OpenBSD/NetBSD ===
+
+You must be running as root to access the hardware OPL directly. You
+can confirm that hadware OPL is working by checking for this message
+on startup:
+
+    OPL_Init: Using driver 'OpenBSD'.
+
+=== FreeBSD ===
+
+There is no native OPL backend for FreeBSD yet.  Sorry!
+
diff --git a/codeblocks/game.cbp b/codeblocks/game.cbp
index bf1c249a..d6313bdf 100644
--- a/codeblocks/game.cbp
+++ b/codeblocks/game.cbp
@@ -46,6 +46,7 @@
 			<Add directory="..\src" />
 			<Add directory="..\textscreen" />
 			<Add directory="..\pcsound" />
+			<Add directory="..\opl" />
 		</Compiler>
 		<Linker>
 			<Add option="-lmingw32 -lSDLmain -lSDL -lSDL_mixer -lSDL_net -mwindows" />
@@ -55,6 +56,36 @@
 		<Unit filename="game-res.rc">
 			<Option compilerVar="WINDRES" />
 		</Unit>
+		<Unit filename="..\opl\fmopl.c">
+			<Option compilerVar="CC" />
+		</Unit>
+		<Unit filename="..\opl\fmopl.h" />
+		<Unit filename="..\opl\ioperm_sys.c">
+			<Option compilerVar="CC" />
+		</Unit>
+		<Unit filename="..\opl\ioperm_sys.h" />
+		<Unit filename="..\opl\opl.c">
+			<Option compilerVar="CC" />
+		</Unit>
+		<Unit filename="..\opl\opl.h" />
+		<Unit filename="..\opl\opl_internal.h" />
+		<Unit filename="..\opl\opl_linux.c">
+			<Option compilerVar="CC" />
+		</Unit>
+		<Unit filename="..\opl\opl_queue.c">
+			<Option compilerVar="CC" />
+		</Unit>
+		<Unit filename="..\opl\opl_queue.h" />
+		<Unit filename="..\opl\opl_sdl.c">
+			<Option compilerVar="CC" />
+		</Unit>
+		<Unit filename="..\opl\opl_timer.c">
+			<Option compilerVar="CC" />
+		</Unit>
+		<Unit filename="..\opl\opl_timer.h" />
+		<Unit filename="..\opl\opl_win32.c">
+			<Option compilerVar="CC" />
+		</Unit>
 		<Unit filename="..\src\am_map.c">
 			<Option compilerVar="CC" />
 		</Unit>
@@ -165,6 +196,9 @@
 		<Unit filename="..\src\i_main.c">
 			<Option compilerVar="CC" />
 		</Unit>
+		<Unit filename="..\src\i_oplmusic.c">
+			<Option compilerVar="CC" />
+		</Unit>
 		<Unit filename="..\src\i_pcsound.c">
 			<Option compilerVar="CC" />
 		</Unit>
@@ -235,6 +269,10 @@
 			<Option compilerVar="CC" />
 		</Unit>
 		<Unit filename="..\src\memio.h" />
+		<Unit filename="..\src\midifile.c">
+			<Option compilerVar="CC" />
+		</Unit>
+		<Unit filename="..\src\midifile.h" />
 		<Unit filename="..\src\mus2mid.c">
 			<Option compilerVar="CC" />
 		</Unit>
diff --git a/configure.in b/configure.in
index 53039e5e..258822ce 100644
--- a/configure.in
+++ b/configure.in
@@ -76,7 +76,13 @@ AC_SDL_MAIN_WORKAROUND([
     AC_CHECK_LIB(samplerate, src_new)
 
     AC_CHECK_HEADERS([linux/kd.h dev/isa/spkrio.h dev/speaker/speaker.h])
-    AC_CHECK_FUNCS(mmap sched_setaffinity)
+    AC_CHECK_FUNCS(mmap sched_setaffinity ioperm)
+
+    # OpenBSD I/O i386 library for I/O port access.
+    # (64 bit has the same thing with a different name!)
+
+    AC_CHECK_LIB(i386, i386_iopl)
+    AC_CHECK_LIB(amd64, amd64_iopl)
 ])
 
 AC_CHECK_TOOL(WINDRES, windres, )
@@ -129,6 +135,8 @@ AC_OUTPUT([
 Makefile
 rpm.spec
 man/Makefile
+opl/Makefile
+opl/examples/Makefile
 pcsound/Makefile
 pkg/Makefile
 pkg/config.make
diff --git a/man/manpage.template b/man/manpage.template
index 052ccb63..41f06dc0 100644
--- a/man/manpage.template
+++ b/man/manpage.template
@@ -28,6 +28,17 @@ specifies a PC speaker driver to use for sound effect playback.  Valid
 options are "Linux" for the Linux console mode driver, "BSD" for the
 NetBSD/OpenBSD PC speaker driver, and "SDL" for SDL-based emulated PC speaker 
 playback (using the digital output).
+.TP
+\fBOPL_DRIVER\fR
+When using OPL MIDI playback, this environment variable specifies an
+OPL backend driver to use.  Valid options are "SDL" for an SDL-based
+software emulated OPL chip, "Linux" for the Linux hardware OPL driver,
+and "OpenBSD" for the OpenBSD/NetBSD hardware OPL driver.
+
+Generally speaking, a real hardware OPL chip sounds better than software
+emulation; however, modern machines do not often include one.  If
+present, it may still require extra work to set up and elevated
+security privileges to access.
 .SH FILES
 .TP
 \fB$HOME/.chocolate-doom/default.cfg\fR
diff --git a/opl/.gitignore b/opl/.gitignore
new file mode 100644
index 00000000..e64379dc
--- /dev/null
+++ b/opl/.gitignore
@@ -0,0 +1,5 @@
+Makefile.in
+Makefile
+.deps
+libopl.a
+*.rc
diff --git a/opl/Makefile.am b/opl/Makefile.am
new file mode 100644
index 00000000..d099b875
--- /dev/null
+++ b/opl/Makefile.am
@@ -0,0 +1,19 @@
+
+AM_CFLAGS=@SDLMIXER_CFLAGS@
+
+SUBDIRS = . examples
+
+noinst_LIBRARIES=libopl.a
+
+libopl_a_SOURCES =                                \
+                            opl_internal.h        \
+        opl.c               opl.h                 \
+        opl_linux.c                               \
+        opl_obsd.c                                \
+        opl_queue.c         opl_queue.h           \
+        opl_sdl.c                                 \
+        opl_timer.c         opl_timer.h           \
+        opl_win32.c                               \
+        ioperm_sys.c        ioperm_sys.h          \
+        fmopl.c             fmopl.h
+
diff --git a/opl/examples/.gitignore b/opl/examples/.gitignore
new file mode 100644
index 00000000..49bb1af8
--- /dev/null
+++ b/opl/examples/.gitignore
@@ -0,0 +1,5 @@
+Makefile.in
+Makefile
+.deps
+droplay
+
diff --git a/opl/examples/Makefile.am b/opl/examples/Makefile.am
new file mode 100644
index 00000000..7c2c7c8a
--- /dev/null
+++ b/opl/examples/Makefile.am
@@ -0,0 +1,8 @@
+
+AM_CFLAGS = -I..
+
+noinst_PROGRAMS=droplay
+
+droplay_LDADD = ../libopl.a @LDFLAGS@ @SDL_LIBS@ @SDLMIXER_LIBS@
+droplay_SOURCES = droplay.c
+
diff --git a/opl/examples/droplay.c b/opl/examples/droplay.c
new file mode 100644
index 00000000..36f5c3c0
--- /dev/null
+++ b/opl/examples/droplay.c
@@ -0,0 +1,217 @@
+// Emacs style mode select   -*- C++ -*- 
+//-----------------------------------------------------------------------------
+//
+// Copyright(C) 2009 Simon Howard
+//
+// This program is free software; you can redistribute it and/or
+// modify it under the terms of the GNU General Public License
+// as published by the Free Software Foundation; either version 2
+// of the License, or (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with this program; if not, write to the Free Software
+// Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
+// 02111-1307, USA.
+//
+// DESCRIPTION:
+//     Demonstration program for OPL library to play back DRO
+//     format files.
+//
+//-----------------------------------------------------------------------------
+
+
+#include <stdio.h>
+#include <stdlib.h>
+
+#include "SDL.h"
+
+#include "opl.h"
+
+#define HEADER_STRING "DBRAWOPL"
+#define ADLIB_PORT 0x388
+
+void WriteReg(unsigned int reg, unsigned int val)
+{
+    int i;
+
+    // This was recorded from an OPL2, but we are probably playing
+    // back on an OPL3, so we need to enable the original OPL2
+    // channels.  Doom does this already, but other games don't.
+
+    if ((reg & 0xf0) == OPL_REGS_FEEDBACK)
+    {
+        val |= 0x30;
+    }
+
+    OPL_WritePort(OPL_REGISTER_PORT, reg);
+
+    for (i=0; i<6; ++i)
+    {
+        OPL_ReadPort(OPL_REGISTER_PORT);
+    }
+
+    OPL_WritePort(OPL_DATA_PORT, val);
+
+    for (i=0; i<35; ++i)
+    {
+        OPL_ReadPort(OPL_REGISTER_PORT);
+    }
+}
+
+void ClearAllRegs(void)
+{
+    int i;
+
+    for (i=0; i<=0xff; ++i)
+    {
+	WriteReg(i, 0x00);
+    }
+}
+
+void Init(void)
+{
+    if (SDL_Init(SDL_INIT_TIMER) < 0)
+    {
+        fprintf(stderr, "Unable to initialise SDL timer\n");
+        exit(-1);
+    }
+
+    if (!OPL_Init(ADLIB_PORT))
+    {
+        fprintf(stderr, "Unable to initialise OPL layer\n");
+        exit(-1);
+    }
+}
+
+void Shutdown(void)
+{
+    OPL_Shutdown();
+}
+
+struct timer_data
+{
+    int running;
+    FILE *fstream;
+};
+
+void TimerCallback(void *data)
+{
+    struct timer_data *timer_data = data;
+    int delay;
+
+    if (!timer_data->running)
+    {
+        return;
+    }
+
+    // Read data until we must make a delay.
+
+    for (;;)
+    {
+        int reg, val;
+
+        // End of file?
+
+        if (feof(timer_data->fstream))
+        {
+            timer_data->running = 0;
+            return;
+        }
+
+        reg = fgetc(timer_data->fstream);
+        val = fgetc(timer_data->fstream);
+
+        // Register value of 0 or 1 indicates a delay.
+
+        if (reg == 0x00)
+        {
+            delay = val;
+            break;
+        }
+        else if (reg == 0x01)
+        {
+            val |= (fgetc(timer_data->fstream) << 8);
+            delay = val;
+            break;
+        }
+        else
+        {
+            WriteReg(reg, val);
+        }
+    }
+
+    // Schedule the next timer callback.
+
+    OPL_SetCallback(delay, TimerCallback, timer_data);
+}
+
+void PlayFile(char *filename)
+{
+    struct timer_data timer_data;
+    int running;
+    char buf[8];
+
+    timer_data.fstream = fopen(filename, "rb");
+
+    if (timer_data.fstream == NULL)
+    {
+        fprintf(stderr, "Failed to open %s\n", filename);
+        exit(-1);
+    }
+
+    if (fread(buf, 1, 8, timer_data.fstream) < 8)
+    {
+        fprintf(stderr, "failed to read raw OPL header\n");
+        exit(-1);
+    }
+
+    if (strncmp(buf, HEADER_STRING, 8) != 0)
+    {
+        fprintf(stderr, "Raw OPL header not found\n");
+        exit(-1);
+    }
+
+    fseek(timer_data.fstream, 28, SEEK_SET);
+    timer_data.running = 1;
+
+    // Start callback loop sequence.
+
+    OPL_SetCallback(0, TimerCallback, &timer_data);
+
+    // Sleep until the playback finishes.
+
+    do
+    {
+        OPL_Lock();
+        running = timer_data.running;
+        OPL_Unlock();
+
+        SDL_Delay(100);
+    } while (running);
+
+    fclose(timer_data.fstream);
+}
+
+int main(int argc, char *argv[])
+{
+    if (argc < 2)
+    {
+        printf("Usage: %s <filename>\n", argv[0]);
+        exit(-1);
+    }
+
+    Init();
+
+    PlayFile(argv[1]);
+
+    ClearAllRegs();
+    Shutdown();
+
+    return 0;
+}
+
diff --git a/opl/fmopl.c b/opl/fmopl.c
new file mode 100644
index 00000000..1671244e
--- /dev/null
+++ b/opl/fmopl.c
@@ -0,0 +1,1155 @@
+/* This file is derived from fmopl.cpp from ScummVM.
+ *
+ * ScummVM is the legal property of its developers, whose names
+ * are too numerous to list here. Please refer to the COPYRIGHT
+ * file distributed with this source distribution.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ *
+ * LGPL licensed version of MAMEs fmopl (V0.37a modified) by
+ * Tatsuyuki Satoh. Included from LGPL'ed AdPlug.
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <stdarg.h>
+#include <math.h>
+
+#include "fmopl.h"
+
+#define PI 3.1415926539
+
+#define CLIP(value, min, max)                      \
+    ( (value) < (min) ? (min) :                    \
+      (value) > (max) ? (max) : (value) )
+
+/* -------------------- preliminary define section --------------------- */
+/* attack/decay rate time rate */
+#define OPL_ARRATE     141280  /* RATE 4 =  2826.24ms @ 3.6MHz */
+#define OPL_DRRATE    1956000  /* RATE 4 = 39280.64ms @ 3.6MHz */
+
+#define FREQ_BITS 24			/* frequency turn          */
+
+/* counter bits = 20 , octerve 7 */
+#define FREQ_RATE   (1<<(FREQ_BITS-20))
+#define TL_BITS    (FREQ_BITS+2)
+
+/* final output shift , limit minimum and maximum */
+#define OPL_OUTSB   (TL_BITS+3-16)		/* OPL output final shift 16bit */
+#define OPL_MAXOUT (0x7fff<<OPL_OUTSB)
+#define OPL_MINOUT (-0x8000<<OPL_OUTSB)
+
+/* -------------------- quality selection --------------------- */
+
+/* sinwave entries */
+/* used static memory = SIN_ENT * 4 (byte) */
+#define SIN_ENT_SHIFT 11
+#define SIN_ENT (1<<SIN_ENT_SHIFT)
+
+/* output level entries (envelope,sinwave) */
+/* envelope counter lower bits */
+static int ENV_BITS;
+/* envelope output entries */
+static int EG_ENT;
+
+/* used dynamic memory = EG_ENT*4*4(byte)or EG_ENT*6*4(byte) */
+/* used static  memory = EG_ENT*4 (byte)                     */
+static int EG_OFF;								 /* OFF */
+static int EG_DED;
+static int EG_DST;								 /* DECAY START */
+static int EG_AED;
+#define EG_AST   0                       /* ATTACK START */
+
+#define EG_STEP (96.0/EG_ENT) /* OPL is 0.1875 dB step  */
+
+/* LFO table entries */
+#define VIB_ENT 512
+#define VIB_SHIFT (32-9)
+#define AMS_ENT 512
+#define AMS_SHIFT (32-9)
+
+#define VIB_RATE_SHIFT 8
+#define VIB_RATE (1<<VIB_RATE_SHIFT)
+
+/* -------------------- local defines , macros --------------------- */
+
+/* register number to channel number , slot offset */
+#define SLOT1 0
+#define SLOT2 1
+
+/* envelope phase */
+#define ENV_MOD_RR  0x00
+#define ENV_MOD_DR  0x01
+#define ENV_MOD_AR  0x02
+
+/* -------------------- tables --------------------- */
+static const int slot_array[32] = {
+	 0, 2, 4, 1, 3, 5,-1,-1,
+	 6, 8,10, 7, 9,11,-1,-1,
+	12,14,16,13,15,17,-1,-1,
+	-1,-1,-1,-1,-1,-1,-1,-1
+};
+
+static uint32_t KSL_TABLE[8 * 16];
+
+static const double KSL_TABLE_SEED[8 * 16] = {
+	/* OCT 0 */
+	0.000, 0.000, 0.000, 0.000,
+	0.000, 0.000, 0.000, 0.000,
+	0.000, 0.000, 0.000, 0.000,
+	0.000, 0.000, 0.000, 0.000,
+	/* OCT 1 */
+	0.000, 0.000, 0.000, 0.000,
+	0.000, 0.000, 0.000, 0.000,
+	0.000, 0.750, 1.125, 1.500,
+	1.875, 2.250, 2.625, 3.000,
+	/* OCT 2 */
+	0.000, 0.000, 0.000, 0.000,
+	0.000, 1.125, 1.875, 2.625,
+	3.000, 3.750, 4.125, 4.500,
+	4.875, 5.250, 5.625, 6.000,
+	/* OCT 3 */
+	0.000, 0.000, 0.000, 1.875,
+	3.000, 4.125, 4.875, 5.625,
+	6.000, 6.750, 7.125, 7.500,
+	7.875, 8.250, 8.625, 9.000,
+	/* OCT 4 */
+	0.000, 0.000, 3.000, 4.875,
+	6.000, 7.125, 7.875, 8.625,
+	9.000, 9.750, 10.125, 10.500,
+	10.875, 11.250, 11.625, 12.000,
+	/* OCT 5 */
+	0.000, 3.000, 6.000, 7.875,
+	9.000, 10.125, 10.875, 11.625,
+	12.000, 12.750, 13.125, 13.500,
+	13.875, 14.250, 14.625, 15.000,
+	/* OCT 6 */
+	0.000, 6.000, 9.000, 10.875,
+	12.000, 13.125, 13.875, 14.625,
+	15.000, 15.750, 16.125, 16.500,
+	16.875, 17.250, 17.625, 18.000,
+	/* OCT 7 */
+	0.000, 9.000, 12.000, 13.875,
+	15.000, 16.125, 16.875, 17.625,
+	18.000, 18.750, 19.125, 19.500,
+	19.875, 20.250, 20.625, 21.000
+};
+
+/* sustain level table (3db per step) */
+/* 0 - 15: 0, 3, 6, 9,12,15,18,21,24,27,30,33,36,39,42,93 (dB)*/
+
+static int SL_TABLE[16];
+
+static const uint32_t SL_TABLE_SEED[16] = {
+	0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 31
+};
+
+#define TL_MAX (EG_ENT * 2) /* limit(tl + ksr + envelope) + sinwave */
+/* TotalLevel : 48 24 12  6  3 1.5 0.75 (dB) */
+/* TL_TABLE[ 0      to TL_MAX          ] : plus  section */
+/* TL_TABLE[ TL_MAX to TL_MAX+TL_MAX-1 ] : minus section */
+static int *TL_TABLE;
+
+/* pointers to TL_TABLE with sinwave output offset */
+static int **SIN_TABLE;
+
+/* LFO table */
+static int *AMS_TABLE;
+static int *VIB_TABLE;
+
+/* envelope output curve table */
+/* attack + decay + OFF */
+//static int ENV_CURVE[2*EG_ENT+1];
+//static int ENV_CURVE[2 * 4096 + 1];   // to keep it static ...
+static int *ENV_CURVE;
+
+
+/* multiple table */
+#define ML(a) (int)(a * 2)
+static const uint32_t MUL_TABLE[16]= {
+/* 1/2, 1, 2, 3, 4, 5, 6, 7, 8, 9,10,11,12,13,14,15 */
+	ML(0.50), ML(1.00), ML(2.00),  ML(3.00), ML(4.00), ML(5.00), ML(6.00), ML(7.00),
+	ML(8.00), ML(9.00), ML(10.00), ML(10.00),ML(12.00),ML(12.00),ML(15.00),ML(15.00)
+};
+#undef ML
+
+/* dummy attack / decay rate ( when rate == 0 ) */
+static int RATE_0[16]=
+{0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0};
+
+/* -------------------- static state --------------------- */
+
+/* lock level of common table */
+static int num_lock = 0;
+
+/* work table */
+static void *cur_chip = NULL;	/* current chip point */
+/* currenct chip state */
+/* static OPLSAMPLE  *bufL,*bufR; */
+static OPL_CH *S_CH;
+static OPL_CH *E_CH;
+static OPL_SLOT *SLOT7_1, *SLOT7_2, *SLOT8_1, *SLOT8_2;
+
+static int outd[1];
+static int ams;
+static int vib;
+static int *ams_table;
+static int *vib_table;
+static int amsIncr;
+static int vibIncr;
+static int feedback2;		/* connect for SLOT 2 */
+
+/* --------------------- rebuild tables ------------------- */
+
+#define ARRAYSIZE(x) (sizeof(x) / sizeof(*x))
+#define SC_KSL(mydb) ((uint32_t) (mydb / (EG_STEP / 2)))
+#define SC_SL(db) (int)(db * ((3 / EG_STEP) * (1 << ENV_BITS))) + EG_DST
+
+void OPLBuildTables(int ENV_BITS_PARAM, int EG_ENT_PARAM) {
+	int i;
+
+	ENV_BITS = ENV_BITS_PARAM;
+	EG_ENT = EG_ENT_PARAM;
+	EG_OFF = ((2 * EG_ENT)<<ENV_BITS);  /* OFF          */
+	EG_DED = EG_OFF;
+	EG_DST = (EG_ENT << ENV_BITS);     /* DECAY  START */
+	EG_AED = EG_DST;
+	//EG_STEP = (96.0/EG_ENT);
+
+	for (i = 0; i < ARRAYSIZE(KSL_TABLE_SEED); i++)
+		KSL_TABLE[i] = SC_KSL(KSL_TABLE_SEED[i]);
+
+	for (i = 0; i < ARRAYSIZE(SL_TABLE_SEED); i++)
+		SL_TABLE[i] = SC_SL(SL_TABLE_SEED[i]);
+}
+
+#undef SC_KSL
+#undef SC_SL
+
+/* --------------------- subroutines  --------------------- */
+
+/* status set and IRQ handling */
+static inline void OPL_STATUS_SET(FM_OPL *OPL, int flag) {
+	/* set status flag */
+	OPL->status |= flag;
+	if(!(OPL->status & 0x80)) {
+		if(OPL->status & OPL->statusmask) {	/* IRQ on */
+			OPL->status |= 0x80;
+			/* callback user interrupt handler (IRQ is OFF to ON) */
+			if(OPL->IRQHandler)
+				(OPL->IRQHandler)(OPL->IRQParam,1);
+		}
+	}
+}
+
+/* status reset and IRQ handling */
+static inline void OPL_STATUS_RESET(FM_OPL *OPL, int flag) {
+	/* reset status flag */
+	OPL->status &= ~flag;
+	if((OPL->status & 0x80)) {
+		if (!(OPL->status & OPL->statusmask)) {
+			OPL->status &= 0x7f;
+			/* callback user interrupt handler (IRQ is ON to OFF) */
+			if(OPL->IRQHandler) (OPL->IRQHandler)(OPL->IRQParam,0);
+		}
+	}
+}
+
+/* IRQ mask set */
+static inline void OPL_STATUSMASK_SET(FM_OPL *OPL, int flag) {
+	OPL->statusmask = flag;
+	/* IRQ handling check */
+	OPL_STATUS_SET(OPL,0);
+	OPL_STATUS_RESET(OPL,0);
+}
+
+/* ----- key on  ----- */
+static inline void OPL_KEYON(OPL_SLOT *SLOT) {
+	/* sin wave restart */
+	SLOT->Cnt = 0;
+	/* set attack */
+	SLOT->evm = ENV_MOD_AR;
+	SLOT->evs = SLOT->evsa;
+	SLOT->evc = EG_AST;
+	SLOT->eve = EG_AED;
+}
+
+/* ----- key off ----- */
+static inline void OPL_KEYOFF(OPL_SLOT *SLOT) {
+	if( SLOT->evm > ENV_MOD_RR) {
+		/* set envelope counter from envleope output */
+
+		// WORKAROUND: The Kyra engine does something very strange when
+		// starting a new song. For each channel:
+		//
+		// * The release rate is set to "fastest".
+		// * Any note is keyed off.
+		// * A very low-frequency note is keyed on.
+		//
+		// Usually, what happens next is that the real notes is keyed
+		// on immediately, in which case there's no problem.
+		//
+		// However, if the note is again keyed off (because the channel
+		// begins on a rest rather than a note), the envelope counter
+		// was moved from the very lowest point on the attack curve to
+		// the very highest point on the release curve.
+		//
+		// Again, this might not be a problem, if the release rate is
+		// still set to "fastest". But in many cases, it had already
+		// been increased. And, possibly because of inaccuracies in the
+		// envelope generator, that would cause the note to "fade out"
+		// for quite a long time.
+		//
+		// What we really need is a way to find the correct starting
+		// point for the envelope counter, and that may be what the
+		// commented-out line below is meant to do. For now, simply
+		// handle the pathological case.
+
+		if (SLOT->evm == ENV_MOD_AR && SLOT->evc == EG_AST)
+			SLOT->evc = EG_DED;
+		else if( !(SLOT->evc & EG_DST) )
+			//SLOT->evc = (ENV_CURVE[SLOT->evc>>ENV_BITS]<<ENV_BITS) + EG_DST;
+			SLOT->evc = EG_DST;
+		SLOT->eve = EG_DED;
+		SLOT->evs = SLOT->evsr;
+		SLOT->evm = ENV_MOD_RR;
+	}
+}
+
+/* ---------- calcrate Envelope Generator & Phase Generator ---------- */
+
+/* return : envelope output */
+static inline uint32_t OPL_CALC_SLOT(OPL_SLOT *SLOT) {
+	/* calcrate envelope generator */
+	if((SLOT->evc += SLOT->evs) >= SLOT->eve) {
+		switch( SLOT->evm ) {
+		case ENV_MOD_AR: /* ATTACK -> DECAY1 */
+			/* next DR */
+			SLOT->evm = ENV_MOD_DR;
+			SLOT->evc = EG_DST;
+			SLOT->eve = SLOT->SL;
+			SLOT->evs = SLOT->evsd;
+			break;
+		case ENV_MOD_DR: /* DECAY -> SL or RR */
+			SLOT->evc = SLOT->SL;
+			SLOT->eve = EG_DED;
+			if(SLOT->eg_typ) {
+				SLOT->evs = 0;
+			} else {
+				SLOT->evm = ENV_MOD_RR;
+				SLOT->evs = SLOT->evsr;
+			}
+			break;
+		case ENV_MOD_RR: /* RR -> OFF */
+			SLOT->evc = EG_OFF;
+			SLOT->eve = EG_OFF + 1;
+			SLOT->evs = 0;
+			break;
+		}
+	}
+	/* calcrate envelope */
+	return SLOT->TLL + ENV_CURVE[SLOT->evc>>ENV_BITS] + (SLOT->ams ? ams : 0);
+}
+
+/* set algorythm connection */
+static void set_algorythm(OPL_CH *CH) {
+	int *carrier = &outd[0];
+	CH->connect1 = CH->CON ? carrier : &feedback2;
+	CH->connect2 = carrier;
+}
+
+/* ---------- frequency counter for operater update ---------- */
+static inline void CALC_FCSLOT(OPL_CH *CH, OPL_SLOT *SLOT) {
+	int ksr;
+
+	/* frequency step counter */
+	SLOT->Incr = CH->fc * SLOT->mul;
+	ksr = CH->kcode >> SLOT->KSR;
+
+	if( SLOT->ksr != ksr ) {
+		SLOT->ksr = ksr;
+		/* attack , decay rate recalcration */
+		SLOT->evsa = SLOT->AR[ksr];
+		SLOT->evsd = SLOT->DR[ksr];
+		SLOT->evsr = SLOT->RR[ksr];
+	}
+	SLOT->TLL = SLOT->TL + (CH->ksl_base>>SLOT->ksl);
+}
+
+/* set multi,am,vib,EG-TYP,KSR,mul */
+static inline void set_mul(FM_OPL *OPL, int slot, int v) {
+	OPL_CH   *CH   = &OPL->P_CH[slot>>1];
+	OPL_SLOT *SLOT = &CH->SLOT[slot & 1];
+
+	SLOT->mul    = MUL_TABLE[v & 0x0f];
+	SLOT->KSR    = (v & 0x10) ? 0 : 2;
+	SLOT->eg_typ = (v & 0x20) >> 5;
+	SLOT->vib    = (v & 0x40);
+	SLOT->ams    = (v & 0x80);
+	CALC_FCSLOT(CH, SLOT);
+}
+
+/* set ksl & tl */
+static inline void set_ksl_tl(FM_OPL *OPL, int slot, int v) {
+	OPL_CH   *CH   = &OPL->P_CH[slot>>1];
+	OPL_SLOT *SLOT = &CH->SLOT[slot & 1];
+	int ksl = v >> 6; /* 0 / 1.5 / 3 / 6 db/OCT */
+
+	SLOT->ksl = ksl ? 3-ksl : 31;
+	SLOT->TL  = (int)((v & 0x3f) * (0.75 / EG_STEP)); /* 0.75db step */
+
+	if(!(OPL->mode & 0x80)) {	/* not CSM latch total level */
+		SLOT->TLL = SLOT->TL + (CH->ksl_base >> SLOT->ksl);
+	}
+}
+
+/* set attack rate & decay rate  */
+static inline void set_ar_dr(FM_OPL *OPL, int slot, int v) {
+	OPL_CH   *CH   = &OPL->P_CH[slot>>1];
+	OPL_SLOT *SLOT = &CH->SLOT[slot & 1];
+	int ar = v >> 4;
+	int dr = v & 0x0f;
+
+	SLOT->AR = ar ? &OPL->AR_TABLE[ar << 2] : RATE_0;
+	SLOT->evsa = SLOT->AR[SLOT->ksr];
+	if(SLOT->evm == ENV_MOD_AR)
+		SLOT->evs = SLOT->evsa;
+
+	SLOT->DR = dr ? &OPL->DR_TABLE[dr<<2] : RATE_0;
+	SLOT->evsd = SLOT->DR[SLOT->ksr];
+	if(SLOT->evm == ENV_MOD_DR)
+		SLOT->evs = SLOT->evsd;
+}
+
+/* set sustain level & release rate */
+static inline void set_sl_rr(FM_OPL *OPL, int slot, int v) {
+	OPL_CH   *CH   = &OPL->P_CH[slot>>1];
+	OPL_SLOT *SLOT = &CH->SLOT[slot & 1];
+	int sl = v >> 4;
+	int rr = v & 0x0f;
+
+	SLOT->SL = SL_TABLE[sl];
+	if(SLOT->evm == ENV_MOD_DR)
+		SLOT->eve = SLOT->SL;
+	SLOT->RR = &OPL->DR_TABLE[rr<<2];
+	SLOT->evsr = SLOT->RR[SLOT->ksr];
+	if(SLOT->evm == ENV_MOD_RR)
+		SLOT->evs = SLOT->evsr;
+}
+
+/* operator output calcrator */
+
+#define OP_OUT(slot,env,con)   slot->wavetable[((slot->Cnt + con)>>(24-SIN_ENT_SHIFT)) & (SIN_ENT-1)][env]
+/* ---------- calcrate one of channel ---------- */
+static inline void OPL_CALC_CH(OPL_CH *CH) {
+	uint32_t env_out;
+	OPL_SLOT *SLOT;
+
+	feedback2 = 0;
+	/* SLOT 1 */
+	SLOT = &CH->SLOT[SLOT1];
+	env_out=OPL_CALC_SLOT(SLOT);
+	if(env_out < (uint32_t)(EG_ENT - 1)) {
+		/* PG */
+		if(SLOT->vib)
+			SLOT->Cnt += (SLOT->Incr * vib) >> VIB_RATE_SHIFT;
+		else
+			SLOT->Cnt += SLOT->Incr;
+		/* connection */
+		if(CH->FB) {
+			int feedback1 = (CH->op1_out[0] + CH->op1_out[1]) >> CH->FB;
+			CH->op1_out[1] = CH->op1_out[0];
+			*CH->connect1 += CH->op1_out[0] = OP_OUT(SLOT, env_out, feedback1);
+		} else {
+			*CH->connect1 += OP_OUT(SLOT, env_out, 0);
+		}
+	} else {
+		CH->op1_out[1] = CH->op1_out[0];
+		CH->op1_out[0] = 0;
+	}
+	/* SLOT 2 */
+	SLOT = &CH->SLOT[SLOT2];
+	env_out=OPL_CALC_SLOT(SLOT);
+	if(env_out < (uint32_t)(EG_ENT - 1)) {
+		/* PG */
+		if(SLOT->vib)
+			SLOT->Cnt += (SLOT->Incr * vib) >> VIB_RATE_SHIFT;
+		else
+			SLOT->Cnt += SLOT->Incr;
+		/* connection */
+		outd[0] += OP_OUT(SLOT, env_out, feedback2);
+	}
+}
+
+/* ---------- calcrate rythm block ---------- */
+#define WHITE_NOISE_db 6.0
+static inline void OPL_CALC_RH(FM_OPL *OPL, OPL_CH *CH) {
+	uint32_t env_tam, env_sd, env_top, env_hh;
+	// This code used to do int(OPL->rnd.getRandomBit() * (WHITE_NOISE_db / EG_STEP)),
+	// but EG_STEP = 96.0/EG_ENT, and WHITE_NOISE_db=6.0. So, that's equivalent to
+	// int(OPL->rnd.getRandomBit() * EG_ENT/16). We know that EG_ENT is 4096, or 1024,
+	// or 128, so we can safely avoid any FP ops.
+	int whitenoise = (rand() & 1) * (EG_ENT>>4);
+
+	int tone8;
+
+	OPL_SLOT *SLOT;
+	int env_out;
+
+	/* BD : same as FM serial mode and output level is large */
+	feedback2 = 0;
+	/* SLOT 1 */
+	SLOT = &CH[6].SLOT[SLOT1];
+	env_out = OPL_CALC_SLOT(SLOT);
+	if(env_out < EG_ENT-1) {
+		/* PG */
+		if(SLOT->vib)
+			SLOT->Cnt += (SLOT->Incr * vib) >> VIB_RATE_SHIFT;
+		else
+			SLOT->Cnt += SLOT->Incr;
+		/* connection */
+		if(CH[6].FB) {
+			int feedback1 = (CH[6].op1_out[0] + CH[6].op1_out[1]) >> CH[6].FB;
+			CH[6].op1_out[1] = CH[6].op1_out[0];
+			feedback2 = CH[6].op1_out[0] = OP_OUT(SLOT, env_out, feedback1);
+		}
+		else {
+			feedback2 = OP_OUT(SLOT, env_out, 0);
+		}
+	} else {
+		feedback2 = 0;
+		CH[6].op1_out[1] = CH[6].op1_out[0];
+		CH[6].op1_out[0] = 0;
+	}
+	/* SLOT 2 */
+	SLOT = &CH[6].SLOT[SLOT2];
+	env_out = OPL_CALC_SLOT(SLOT);
+	if(env_out < EG_ENT-1) {
+		/* PG */
+		if(SLOT->vib)
+			SLOT->Cnt += (SLOT->Incr * vib) >> VIB_RATE_SHIFT;
+		else
+			SLOT->Cnt += SLOT->Incr;
+		/* connection */
+		outd[0] += OP_OUT(SLOT, env_out, feedback2) * 2;
+	}
+
+	// SD  (17) = mul14[fnum7] + white noise
+	// TAM (15) = mul15[fnum8]
+	// TOP (18) = fnum6(mul18[fnum8]+whitenoise)
+	// HH  (14) = fnum7(mul18[fnum8]+whitenoise) + white noise
+	env_sd = OPL_CALC_SLOT(SLOT7_2) + whitenoise;
+	env_tam =OPL_CALC_SLOT(SLOT8_1);
+	env_top = OPL_CALC_SLOT(SLOT8_2);
+	env_hh = OPL_CALC_SLOT(SLOT7_1) + whitenoise;
+
+	/* PG */
+	if(SLOT7_1->vib)
+		SLOT7_1->Cnt += (SLOT7_1->Incr * vib) >> (VIB_RATE_SHIFT-1);
+	else
+		SLOT7_1->Cnt += 2 * SLOT7_1->Incr;
+	if(SLOT7_2->vib)
+		SLOT7_2->Cnt += (CH[7].fc * vib) >> (VIB_RATE_SHIFT-3);
+	else
+		SLOT7_2->Cnt += (CH[7].fc * 8);
+	if(SLOT8_1->vib)
+		SLOT8_1->Cnt += (SLOT8_1->Incr * vib) >> VIB_RATE_SHIFT;
+	else
+		SLOT8_1->Cnt += SLOT8_1->Incr;
+	if(SLOT8_2->vib)
+		SLOT8_2->Cnt += ((CH[8].fc * 3) * vib) >> (VIB_RATE_SHIFT-4);
+	else
+		SLOT8_2->Cnt += (CH[8].fc * 48);
+
+	tone8 = OP_OUT(SLOT8_2,whitenoise,0 );
+
+	/* SD */
+	if(env_sd < (uint32_t)(EG_ENT - 1))
+		outd[0] += OP_OUT(SLOT7_1, env_sd, 0) * 8;
+	/* TAM */
+	if(env_tam < (uint32_t)(EG_ENT - 1))
+		outd[0] += OP_OUT(SLOT8_1, env_tam, 0) * 2;
+	/* TOP-CY */
+	if(env_top < (uint32_t)(EG_ENT - 1))
+		outd[0] += OP_OUT(SLOT7_2, env_top, tone8) * 2;
+	/* HH */
+	if(env_hh  < (uint32_t)(EG_ENT-1))
+		outd[0] += OP_OUT(SLOT7_2, env_hh, tone8) * 2;
+}
+
+/* ----------- initialize time tabls ----------- */
+static void init_timetables(FM_OPL *OPL, int ARRATE, int DRRATE) {
+	int i;
+	double rate;
+
+	/* make attack rate & decay rate tables */
+	for (i = 0; i < 4; i++)
+		OPL->AR_TABLE[i] = OPL->DR_TABLE[i] = 0;
+	for (i = 4; i <= 60; i++) {
+		rate = OPL->freqbase;						/* frequency rate */
+		if(i < 60)
+			rate *= 1.0 + (i & 3) * 0.25;		/* b0-1 : x1 , x1.25 , x1.5 , x1.75 */
+		rate *= 1 << ((i >> 2) - 1);						/* b2-5 : shift bit */
+		rate *= (double)(EG_ENT << ENV_BITS);
+		OPL->AR_TABLE[i] = (int)(rate / ARRATE);
+		OPL->DR_TABLE[i] = (int)(rate / DRRATE);
+	}
+	for (i = 60; i < 76; i++) {
+		OPL->AR_TABLE[i] = EG_AED-1;
+		OPL->DR_TABLE[i] = OPL->DR_TABLE[60];
+	}
+}
+
+/* ---------- generic table initialize ---------- */
+static int OPLOpenTable(void) {
+	int s,t;
+	double rate;
+	int i,j;
+	double pom;
+
+	/* allocate dynamic tables */
+	if((TL_TABLE = (int *)malloc(TL_MAX * 2 * sizeof(int))) == NULL)
+		return 0;
+
+	if((SIN_TABLE = (int **)malloc(SIN_ENT * 4 * sizeof(int *))) == NULL) {
+		free(TL_TABLE);
+		return 0;
+	}
+
+	if((AMS_TABLE = (int *)malloc(AMS_ENT * 2 * sizeof(int))) == NULL) {
+		free(TL_TABLE);
+		free(SIN_TABLE);
+		return 0;
+	}
+
+	if((VIB_TABLE = (int *)malloc(VIB_ENT * 2 * sizeof(int))) == NULL) {
+		free(TL_TABLE);
+		free(SIN_TABLE);
+		free(AMS_TABLE);
+		return 0;
+	}
+	/* make total level table */
+	for (t = 0; t < EG_ENT - 1 ; t++) {
+		rate = ((1 << TL_BITS) - 1) / pow(10.0, EG_STEP * t / 20);	/* dB -> voltage */
+		TL_TABLE[         t] =  (int)rate;
+		TL_TABLE[TL_MAX + t] = -TL_TABLE[t];
+	}
+	/* fill volume off area */
+	for (t = EG_ENT - 1; t < TL_MAX; t++) {
+		TL_TABLE[t] = TL_TABLE[TL_MAX + t] = 0;
+	}
+
+	/* make sinwave table (total level offet) */
+	/* degree 0 = degree 180                   = off */
+	SIN_TABLE[0] = SIN_TABLE[SIN_ENT /2 ] = &TL_TABLE[EG_ENT - 1];
+	for (s = 1;s <= SIN_ENT / 4; s++) {
+		pom = sin(2 * PI * s / SIN_ENT); /* sin     */
+		pom = 20 * log10(1 / pom);	   /* decibel */
+		j = (int) (pom / EG_STEP);         /* TL_TABLE steps */
+
+		/* degree 0   -  90    , degree 180 -  90 : plus section */
+		SIN_TABLE[          s] = SIN_TABLE[SIN_ENT / 2 - s] = &TL_TABLE[j];
+		/* degree 180 - 270    , degree 360 - 270 : minus section */
+		SIN_TABLE[SIN_ENT / 2 + s] = SIN_TABLE[SIN_ENT - s] = &TL_TABLE[TL_MAX + j];
+	}
+	for (s = 0;s < SIN_ENT; s++) {
+		SIN_TABLE[SIN_ENT * 1 + s] = s < (SIN_ENT / 2) ? SIN_TABLE[s] : &TL_TABLE[EG_ENT];
+		SIN_TABLE[SIN_ENT * 2 + s] = SIN_TABLE[s % (SIN_ENT / 2)];
+		SIN_TABLE[SIN_ENT * 3 + s] = (s / (SIN_ENT / 4)) & 1 ? &TL_TABLE[EG_ENT] : SIN_TABLE[SIN_ENT * 2 + s];
+	}
+
+
+	ENV_CURVE = (int *)malloc(sizeof(int) * (2*EG_ENT+1));
+
+	/* envelope counter -> envelope output table */
+	for (i=0; i < EG_ENT; i++) {
+		/* ATTACK curve */
+		pom = pow(((double)(EG_ENT - 1 - i) / EG_ENT), 8) * EG_ENT;
+		/* if( pom >= EG_ENT ) pom = EG_ENT-1; */
+		ENV_CURVE[i] = (int)pom;
+		/* DECAY ,RELEASE curve */
+		ENV_CURVE[(EG_DST >> ENV_BITS) + i]= i;
+	}
+	/* off */
+	ENV_CURVE[EG_OFF >> ENV_BITS]= EG_ENT - 1;
+	/* make LFO ams table */
+	for (i=0; i < AMS_ENT; i++) {
+		pom = (1.0 + sin(2 * PI * i / AMS_ENT)) / 2; /* sin */
+		AMS_TABLE[i]         = (int)((1.0 / EG_STEP) * pom); /* 1dB   */
+		AMS_TABLE[AMS_ENT + i] = (int)((4.8 / EG_STEP) * pom); /* 4.8dB */
+	}
+	/* make LFO vibrate table */
+	for (i=0; i < VIB_ENT; i++) {
+		/* 100cent = 1seminote = 6% ?? */
+		pom = (double)VIB_RATE * 0.06 * sin(2 * PI * i / VIB_ENT); /* +-100sect step */
+		VIB_TABLE[i]         = (int)(VIB_RATE + (pom * 0.07)); /* +- 7cent */
+		VIB_TABLE[VIB_ENT + i] = (int)(VIB_RATE + (pom * 0.14)); /* +-14cent */
+	}
+	return 1;
+}
+
+static void OPLCloseTable(void) {
+	free(TL_TABLE);
+	free(SIN_TABLE);
+	free(AMS_TABLE);
+	free(VIB_TABLE);
+	free(ENV_CURVE);
+}
+
+/* CSM Key Controll */
+static inline void CSMKeyControll(OPL_CH *CH) {
+	OPL_SLOT *slot1 = &CH->SLOT[SLOT1];
+	OPL_SLOT *slot2 = &CH->SLOT[SLOT2];
+	/* all key off */
+	OPL_KEYOFF(slot1);
+	OPL_KEYOFF(slot2);
+	/* total level latch */
+	slot1->TLL = slot1->TL + (CH->ksl_base>>slot1->ksl);
+	slot1->TLL = slot1->TL + (CH->ksl_base>>slot1->ksl);
+	/* key on */
+	CH->op1_out[0] = CH->op1_out[1] = 0;
+	OPL_KEYON(slot1);
+	OPL_KEYON(slot2);
+}
+
+/* ---------- opl initialize ---------- */
+static void OPL_initalize(FM_OPL *OPL) {
+	int fn;
+
+	/* frequency base */
+	OPL->freqbase = (OPL->rate) ? ((double)OPL->clock / OPL->rate) / 72 : 0;
+	/* Timer base time */
+	OPL->TimerBase = 1.0/((double)OPL->clock / 72.0 );
+	/* make time tables */
+	init_timetables(OPL, OPL_ARRATE, OPL_DRRATE);
+	/* make fnumber -> increment counter table */
+	for( fn=0; fn < 1024; fn++) {
+		OPL->FN_TABLE[fn] = (uint32_t)(OPL->freqbase * fn * FREQ_RATE * (1<<7) / 2);
+	}
+	/* LFO freq.table */
+	OPL->amsIncr = (int)(OPL->rate ? (double)AMS_ENT * (1 << AMS_SHIFT) / OPL->rate * 3.7 * ((double)OPL->clock/3600000) : 0);
+	OPL->vibIncr = (int)(OPL->rate ? (double)VIB_ENT * (1 << VIB_SHIFT) / OPL->rate * 6.4 * ((double)OPL->clock/3600000) : 0);
+}
+
+/* ---------- write a OPL registers ---------- */
+void OPLWriteReg(FM_OPL *OPL, int r, int v) {
+	OPL_CH *CH;
+	int slot;
+	uint32_t block_fnum;
+
+	switch(r & 0xe0) {
+	case 0x00: /* 00-1f:controll */
+		switch(r & 0x1f) {
+		case 0x01:
+			/* wave selector enable */
+			if(OPL->type&OPL_TYPE_WAVESEL) {
+				OPL->wavesel = v & 0x20;
+				if(!OPL->wavesel) {
+					/* preset compatible mode */
+					int c;
+					for(c=0; c<OPL->max_ch; c++) {
+						OPL->P_CH[c].SLOT[SLOT1].wavetable = &SIN_TABLE[0];
+						OPL->P_CH[c].SLOT[SLOT2].wavetable = &SIN_TABLE[0];
+					}
+				}
+			}
+			return;
+		case 0x02:	/* Timer 1 */
+			OPL->T[0] = (256-v) * 4;
+			break;
+		case 0x03:	/* Timer 2 */
+			OPL->T[1] = (256-v) * 16;
+			return;
+		case 0x04:	/* IRQ clear / mask and Timer enable */
+			if(v & 0x80) {	/* IRQ flag clear */
+				OPL_STATUS_RESET(OPL, 0x7f);
+			} else {	/* set IRQ mask ,timer enable*/
+				uint8_t st1 = v & 1;
+				uint8_t st2 = (v >> 1) & 1;
+				/* IRQRST,T1MSK,t2MSK,EOSMSK,BRMSK,x,ST2,ST1 */
+				OPL_STATUS_RESET(OPL, v & 0x78);
+				OPL_STATUSMASK_SET(OPL,((~v) & 0x78) | 0x01);
+				/* timer 2 */
+				if(OPL->st[1] != st2) {
+					double interval = st2 ? (double)OPL->T[1] * OPL->TimerBase : 0.0;
+					OPL->st[1] = st2;
+					if (OPL->TimerHandler) (OPL->TimerHandler)(OPL->TimerParam + 1, interval);
+				}
+				/* timer 1 */
+				if(OPL->st[0] != st1) {
+					double interval = st1 ? (double)OPL->T[0] * OPL->TimerBase : 0.0;
+					OPL->st[0] = st1;
+					if (OPL->TimerHandler) (OPL->TimerHandler)(OPL->TimerParam + 0, interval);
+				}
+			}
+			return;
+		}
+		break;
+	case 0x20:	/* am,vib,ksr,eg type,mul */
+		slot = slot_array[r&0x1f];
+		if(slot == -1)
+			return;
+		set_mul(OPL,slot,v);
+		return;
+	case 0x40:
+		slot = slot_array[r&0x1f];
+		if(slot == -1)
+			return;
+		set_ksl_tl(OPL,slot,v);
+		return;
+	case 0x60:
+		slot = slot_array[r&0x1f];
+		if(slot == -1)
+			return;
+		set_ar_dr(OPL,slot,v);
+		return;
+	case 0x80:
+		slot = slot_array[r&0x1f];
+		if(slot == -1)
+			return;
+		set_sl_rr(OPL,slot,v);
+		return;
+	case 0xa0:
+		switch(r) {
+		case 0xbd:
+			/* amsep,vibdep,r,bd,sd,tom,tc,hh */
+			{
+			uint8_t rkey = OPL->rythm ^ v;
+			OPL->ams_table = &AMS_TABLE[v & 0x80 ? AMS_ENT : 0];
+			OPL->vib_table = &VIB_TABLE[v & 0x40 ? VIB_ENT : 0];
+			OPL->rythm  = v & 0x3f;
+			if(OPL->rythm & 0x20) {
+				/* BD key on/off */
+				if(rkey & 0x10) {
+					if(v & 0x10) {
+						OPL->P_CH[6].op1_out[0] = OPL->P_CH[6].op1_out[1] = 0;
+						OPL_KEYON(&OPL->P_CH[6].SLOT[SLOT1]);
+						OPL_KEYON(&OPL->P_CH[6].SLOT[SLOT2]);
+					} else {
+						OPL_KEYOFF(&OPL->P_CH[6].SLOT[SLOT1]);
+						OPL_KEYOFF(&OPL->P_CH[6].SLOT[SLOT2]);
+					}
+				}
+				/* SD key on/off */
+				if(rkey & 0x08) {
+					if(v & 0x08)
+						OPL_KEYON(&OPL->P_CH[7].SLOT[SLOT2]);
+					else
+						OPL_KEYOFF(&OPL->P_CH[7].SLOT[SLOT2]);
+				}/* TAM key on/off */
+				if(rkey & 0x04) {
+					if(v & 0x04)
+						OPL_KEYON(&OPL->P_CH[8].SLOT[SLOT1]);
+					else
+						OPL_KEYOFF(&OPL->P_CH[8].SLOT[SLOT1]);
+				}
+				/* TOP-CY key on/off */
+				if(rkey & 0x02) {
+					if(v & 0x02)
+						OPL_KEYON(&OPL->P_CH[8].SLOT[SLOT2]);
+					else
+						OPL_KEYOFF(&OPL->P_CH[8].SLOT[SLOT2]);
+				}
+				/* HH key on/off */
+				if(rkey & 0x01) {
+					if(v & 0x01)
+						OPL_KEYON(&OPL->P_CH[7].SLOT[SLOT1]);
+					else
+						OPL_KEYOFF(&OPL->P_CH[7].SLOT[SLOT1]);
+				}
+			}
+			}
+			return;
+
+		default:
+			break;
+		}
+		/* keyon,block,fnum */
+		if((r & 0x0f) > 8)
+			return;
+		CH = &OPL->P_CH[r & 0x0f];
+		if(!(r&0x10)) {	/* a0-a8 */
+			block_fnum  = (CH->block_fnum & 0x1f00) | v;
+		} else {	/* b0-b8 */
+			int keyon = (v >> 5) & 1;
+			block_fnum = ((v & 0x1f) << 8) | (CH->block_fnum & 0xff);
+			if(CH->keyon != keyon) {
+				if((CH->keyon=keyon)) {
+					CH->op1_out[0] = CH->op1_out[1] = 0;
+					OPL_KEYON(&CH->SLOT[SLOT1]);
+					OPL_KEYON(&CH->SLOT[SLOT2]);
+				} else {
+					OPL_KEYOFF(&CH->SLOT[SLOT1]);
+					OPL_KEYOFF(&CH->SLOT[SLOT2]);
+				}
+			}
+		}
+		/* update */
+		if(CH->block_fnum != block_fnum) {
+			int blockRv = 7 - (block_fnum >> 10);
+			int fnum = block_fnum & 0x3ff;
+			CH->block_fnum = block_fnum;
+			CH->ksl_base = KSL_TABLE[block_fnum >> 6];
+			CH->fc = OPL->FN_TABLE[fnum] >> blockRv;
+			CH->kcode = CH->block_fnum >> 9;
+			if((OPL->mode & 0x40) && CH->block_fnum & 0x100)
+				CH->kcode |=1;
+			CALC_FCSLOT(CH,&CH->SLOT[SLOT1]);
+			CALC_FCSLOT(CH,&CH->SLOT[SLOT2]);
+		}
+		return;
+	case 0xc0:
+		/* FB,C */
+		if((r & 0x0f) > 8)
+			return;
+		CH = &OPL->P_CH[r&0x0f];
+		{
+			int feedback = (v >> 1) & 7;
+			CH->FB = feedback ? (8 + 1) - feedback : 0;
+			CH->CON = v & 1;
+			set_algorythm(CH);
+		}
+		return;
+	case 0xe0: /* wave type */
+		slot = slot_array[r & 0x1f];
+		if(slot == -1)
+			return;
+		CH = &OPL->P_CH[slot>>1];
+		if(OPL->wavesel) {
+			CH->SLOT[slot&1].wavetable = &SIN_TABLE[(v & 0x03) * SIN_ENT];
+		}
+		return;
+	}
+}
+
+/* lock/unlock for common table */
+static int OPL_LockTable(void) {
+	num_lock++;
+	if(num_lock>1)
+		return 0;
+	/* first time */
+	cur_chip = NULL;
+	/* allocate total level table (128kb space) */
+	if(!OPLOpenTable()) {
+		num_lock--;
+		return -1;
+	}
+	return 0;
+}
+
+static void OPL_UnLockTable(void) {
+	if(num_lock)
+		num_lock--;
+	if(num_lock)
+		return;
+	/* last time */
+	cur_chip = NULL;
+	OPLCloseTable();
+}
+
+/*******************************************************************************/
+/*		YM3812 local section                                                   */
+/*******************************************************************************/
+
+/* ---------- update one of chip ----------- */
+void YM3812UpdateOne(FM_OPL *OPL, int16_t *buffer, int length, int interleave) {
+	int i;
+	int data;
+	int16_t *buf = buffer;
+	uint32_t amsCnt = OPL->amsCnt;
+	uint32_t vibCnt = OPL->vibCnt;
+	uint8_t rythm = OPL->rythm & 0x20;
+	OPL_CH *CH, *R_CH;
+
+
+	if((void *)OPL != cur_chip) {
+		cur_chip = (void *)OPL;
+		/* channel pointers */
+		S_CH = OPL->P_CH;
+		E_CH = &S_CH[9];
+		/* rythm slot */
+		SLOT7_1 = &S_CH[7].SLOT[SLOT1];
+		SLOT7_2 = &S_CH[7].SLOT[SLOT2];
+		SLOT8_1 = &S_CH[8].SLOT[SLOT1];
+		SLOT8_2 = &S_CH[8].SLOT[SLOT2];
+		/* LFO state */
+		amsIncr = OPL->amsIncr;
+		vibIncr = OPL->vibIncr;
+		ams_table = OPL->ams_table;
+		vib_table = OPL->vib_table;
+	}
+	R_CH = rythm ? &S_CH[6] : E_CH;
+	for(i = 0; i < length; i++) {
+		/*            channel A         channel B         channel C      */
+		/* LFO */
+		ams = ams_table[(amsCnt += amsIncr) >> AMS_SHIFT];
+		vib = vib_table[(vibCnt += vibIncr) >> VIB_SHIFT];
+		outd[0] = 0;
+		/* FM part */
+		for(CH=S_CH; CH < R_CH; CH++)
+			OPL_CALC_CH(CH);
+		/* Rythn part */
+		if(rythm)
+			OPL_CALC_RH(OPL, S_CH);
+		/* limit check */
+		data = CLIP(outd[0], OPL_MINOUT, OPL_MAXOUT);
+		/* store to sound buffer */
+		buf[i << interleave] = data >> OPL_OUTSB;
+	}
+
+	OPL->amsCnt = amsCnt;
+	OPL->vibCnt = vibCnt;
+}
+
+/* ---------- reset a chip ---------- */
+void OPLResetChip(FM_OPL *OPL) {
+	int c,s;
+	int i;
+
+	/* reset chip */
+	OPL->mode = 0;	/* normal mode */
+	OPL_STATUS_RESET(OPL, 0x7f);
+	/* reset with register write */
+	OPLWriteReg(OPL, 0x01,0); /* wabesel disable */
+	OPLWriteReg(OPL, 0x02,0); /* Timer1 */
+	OPLWriteReg(OPL, 0x03,0); /* Timer2 */
+	OPLWriteReg(OPL, 0x04,0); /* IRQ mask clear */
+	for(i = 0xff; i >= 0x20; i--)
+		OPLWriteReg(OPL,i,0);
+	/* reset OPerator parameter */
+	for(c = 0; c < OPL->max_ch ;c++ ) {
+		OPL_CH *CH = &OPL->P_CH[c];
+		/* OPL->P_CH[c].PAN = OPN_CENTER; */
+		for(s = 0; s < 2; s++ ) {
+			/* wave table */
+			CH->SLOT[s].wavetable = &SIN_TABLE[0];
+			/* CH->SLOT[s].evm = ENV_MOD_RR; */
+			CH->SLOT[s].evc = EG_OFF;
+			CH->SLOT[s].eve = EG_OFF + 1;
+			CH->SLOT[s].evs = 0;
+		}
+	}
+}
+
+/* ----------  Create a virtual YM3812 ----------       */
+/* 'rate'  is sampling rate and 'bufsiz' is the size of the  */
+FM_OPL *OPLCreate(int type, int clock, int rate) {
+	char *ptr;
+	FM_OPL *OPL;
+	int state_size;
+	int max_ch = 9; /* normaly 9 channels */
+
+	if( OPL_LockTable() == -1)
+		return NULL;
+	/* allocate OPL state space */
+	state_size  = sizeof(FM_OPL);
+	state_size += sizeof(OPL_CH) * max_ch;
+
+	/* allocate memory block */
+	ptr = (char *)calloc(state_size, 1);
+	if(ptr == NULL)
+		return NULL;
+
+	/* clear */
+	memset(ptr, 0, state_size);
+	OPL       = (FM_OPL *)ptr; ptr += sizeof(FM_OPL);
+	OPL->P_CH = (OPL_CH *)ptr; ptr += sizeof(OPL_CH) * max_ch;
+
+	/* set channel state pointer */
+	OPL->type  = type;
+	OPL->clock = clock;
+	OPL->rate  = rate;
+	OPL->max_ch = max_ch;
+
+	/* init grobal tables */
+	OPL_initalize(OPL);
+
+	/* reset chip */
+	OPLResetChip(OPL);
+	return OPL;
+}
+
+/* ----------  Destroy one of vietual YM3812 ----------       */
+void OPLDestroy(FM_OPL *OPL) {
+	OPL_UnLockTable();
+	free(OPL);
+}
+
+/* ----------  Option handlers ----------       */
+void OPLSetTimerHandler(FM_OPL *OPL, OPL_TIMERHANDLER TimerHandler,int channelOffset) {
+	OPL->TimerHandler   = TimerHandler;
+	OPL->TimerParam = channelOffset;
+}
+
+void OPLSetIRQHandler(FM_OPL *OPL, OPL_IRQHANDLER IRQHandler, int param) {
+	OPL->IRQHandler     = IRQHandler;
+	OPL->IRQParam = param;
+}
+
+void OPLSetUpdateHandler(FM_OPL *OPL, OPL_UPDATEHANDLER UpdateHandler,int param) {
+	OPL->UpdateHandler = UpdateHandler;
+	OPL->UpdateParam = param;
+}
+
+/* ---------- YM3812 I/O interface ---------- */
+int OPLWrite(FM_OPL *OPL,int a,int v) {
+	if(!(a & 1)) {	/* address port */
+		OPL->address = v & 0xff;
+	} else {	/* data port */
+		if(OPL->UpdateHandler)
+			OPL->UpdateHandler(OPL->UpdateParam,0);
+		OPLWriteReg(OPL, OPL->address,v);
+	}
+	return OPL->status >> 7;
+}
+
+unsigned char OPLRead(FM_OPL *OPL,int a) {
+	if(!(a & 1)) {	/* status port */
+		return OPL->status & (OPL->statusmask | 0x80);
+	}
+
+	return 0;
+}
+
+int OPLTimerOver(FM_OPL *OPL, int c) {
+	if(c) {	/* Timer B */
+		OPL_STATUS_SET(OPL, 0x20);
+	} else {	/* Timer A */
+		OPL_STATUS_SET(OPL, 0x40);
+		/* CSM mode key,TL controll */
+		if(OPL->mode & 0x80) {	/* CSM mode total level latch and auto key on */
+			int ch;
+			if(OPL->UpdateHandler)
+				OPL->UpdateHandler(OPL->UpdateParam,0);
+			for(ch = 0; ch < 9; ch++)
+				CSMKeyControll(&OPL->P_CH[ch]);
+		}
+	}
+	/* reload timer */
+	if (OPL->TimerHandler)
+		(OPL->TimerHandler)(OPL->TimerParam + c, (double)OPL->T[c] * OPL->TimerBase);
+	return OPL->status >> 7;
+}
+
+FM_OPL *makeAdlibOPL(int rate) {
+	// We need to emulate one YM3812 chip
+	int env_bits = FMOPL_ENV_BITS_HQ;
+	int eg_ent = FMOPL_EG_ENT_HQ;
+
+	OPLBuildTables(env_bits, eg_ent);
+	return OPLCreate(OPL_TYPE_YM3812, 3579545, rate);
+}
+
diff --git a/opl/fmopl.h b/opl/fmopl.h
new file mode 100644
index 00000000..2bbe8363
--- /dev/null
+++ b/opl/fmopl.h
@@ -0,0 +1,167 @@
+/* This file is derived from fmopl.h from ScummVM.
+ *
+ * ScummVM is the legal property of its developers, whose names
+ * are too numerous to list here. Please refer to the COPYRIGHT
+ * file distributed with this source distribution.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ *
+ * LGPL licensed version of MAMEs fmopl (V0.37a modified) by
+ * Tatsuyuki Satoh. Included from LGPL'ed AdPlug.
+ */
+
+
+#ifndef OPL_FMOPL_H
+#define OPL_FMOPL_H
+
+#include "inttypes.h"
+
+enum {
+	FMOPL_ENV_BITS_HQ = 16,
+	FMOPL_ENV_BITS_MQ = 8,
+	FMOPL_ENV_BITS_LQ = 8,
+	FMOPL_EG_ENT_HQ = 4096,
+	FMOPL_EG_ENT_MQ = 1024,
+	FMOPL_EG_ENT_LQ = 128
+};
+
+typedef void (*OPL_TIMERHANDLER)(int channel,double interval_Sec);
+typedef void (*OPL_IRQHANDLER)(int param,int irq);
+typedef void (*OPL_UPDATEHANDLER)(int param,int min_interval_us);
+
+#define OPL_TYPE_WAVESEL   0x01  /* waveform select    */
+
+/* Saving is necessary for member of the 'R' mark for suspend/resume */
+/* ---------- OPL one of slot  ---------- */
+typedef struct fm_opl_slot {
+	int TL;		/* total level     :TL << 8				*/
+	int TLL;	/* adjusted now TL						*/
+	uint8_t KSR;	/* key scale rate  :(shift down bit)	*/
+	int *AR;	/* attack rate     :&AR_TABLE[AR<<2]	*/
+	int *DR;	/* decay rate      :&DR_TABLE[DR<<2]	*/
+	int SL;		/* sustain level   :SL_TABLE[SL]		*/
+	int *RR;	/* release rate    :&DR_TABLE[RR<<2]	*/
+	uint8_t ksl;	/* keyscale level  :(shift down bits)	*/
+	uint8_t ksr;	/* key scale rate  :kcode>>KSR			*/
+	unsigned int mul;	/* multiple        :ML_TABLE[ML]		*/
+	unsigned int Cnt;	/* frequency count						*/
+	unsigned int Incr;	/* frequency step						*/
+
+	/* envelope generator state */
+	uint8_t eg_typ;/* envelope type flag					*/
+	uint8_t evm;	/* envelope phase						*/
+	int evc;	/* envelope counter						*/
+	int eve;	/* envelope counter end point			*/
+	int evs;	/* envelope counter step				*/
+	int evsa;	/* envelope step for AR :AR[ksr]		*/
+	int evsd;	/* envelope step for DR :DR[ksr]		*/
+	int evsr;	/* envelope step for RR :RR[ksr]		*/
+
+	/* LFO */
+	uint8_t ams;		/* ams flag                            */
+	uint8_t vib;		/* vibrate flag                        */
+	/* wave selector */
+	int **wavetable;
+} OPL_SLOT;
+
+/* ---------- OPL one of channel  ---------- */
+typedef struct fm_opl_channel {
+	OPL_SLOT SLOT[2];
+	uint8_t CON;			/* connection type					*/
+	uint8_t FB;			/* feed back       :(shift down bit)*/
+	int *connect1;		/* slot1 output pointer				*/
+	int *connect2;		/* slot2 output pointer				*/
+	int op1_out[2];		/* slot1 output for selfeedback		*/
+
+	/* phase generator state */
+	unsigned int block_fnum;	/* block+fnum						*/
+	uint8_t kcode;		/* key code        : KeyScaleCode	*/
+	unsigned int fc;			/* Freq. Increment base				*/
+	unsigned int ksl_base;		/* KeyScaleLevel Base step			*/
+	uint8_t keyon;		/* key on/off flag					*/
+} OPL_CH;
+
+/* OPL state */
+typedef struct fm_opl_f {
+	uint8_t type;			/* chip type                         */
+	int clock;			/* master clock  (Hz)                */
+	int rate;			/* sampling rate (Hz)                */
+	double freqbase;	/* frequency base                    */
+	double TimerBase;	/* Timer base time (==sampling time) */
+	uint8_t address;		/* address register                  */
+	uint8_t status;		/* status flag                       */
+	uint8_t statusmask;	/* status mask                       */
+	unsigned int mode;			/* Reg.08 : CSM , notesel,etc.       */
+
+	/* Timer */
+	int T[2];			/* timer counter                     */
+	uint8_t st[2];		/* timer enable                      */
+
+	/* FM channel slots */
+	OPL_CH *P_CH;		/* pointer of CH                     */
+	int	max_ch;			/* maximum channel                   */
+
+	/* Rythm sention */
+	uint8_t rythm;		/* Rythm mode , key flag */
+
+	/* time tables */
+	int AR_TABLE[76];	/* atttack rate tables				*/
+	int DR_TABLE[76];	/* decay rate tables				*/
+	unsigned int FN_TABLE[1024];/* fnumber -> increment counter		*/
+
+	/* LFO */
+	int *ams_table;
+	int *vib_table;
+	int amsCnt;
+	int amsIncr;
+	int vibCnt;
+	int vibIncr;
+
+	/* wave selector enable flag */
+	uint8_t wavesel;
+
+	/* external event callback handler */
+	OPL_TIMERHANDLER  TimerHandler;		/* TIMER handler   */
+	int TimerParam;						/* TIMER parameter */
+	OPL_IRQHANDLER    IRQHandler;		/* IRQ handler    */
+	int IRQParam;						/* IRQ parameter  */
+	OPL_UPDATEHANDLER UpdateHandler;	/* stream update handler   */
+	int UpdateParam;					/* stream update parameter */
+} FM_OPL;
+
+/* ---------- Generic interface section ---------- */
+#define OPL_TYPE_YM3526 (0)
+#define OPL_TYPE_YM3812 (OPL_TYPE_WAVESEL)
+
+void OPLBuildTables(int ENV_BITS_PARAM, int EG_ENT_PARAM);
+
+FM_OPL *OPLCreate(int type, int clock, int rate);
+void OPLDestroy(FM_OPL *OPL);
+void OPLSetTimerHandler(FM_OPL *OPL, OPL_TIMERHANDLER TimerHandler, int channelOffset);
+void OPLSetIRQHandler(FM_OPL *OPL, OPL_IRQHANDLER IRQHandler, int param);
+void OPLSetUpdateHandler(FM_OPL *OPL, OPL_UPDATEHANDLER UpdateHandler, int param);
+
+void OPLResetChip(FM_OPL *OPL);
+int OPLWrite(FM_OPL *OPL, int a, int v);
+unsigned char OPLRead(FM_OPL *OPL, int a);
+int OPLTimerOver(FM_OPL *OPL, int c);
+void OPLWriteReg(FM_OPL *OPL, int r, int v);
+void YM3812UpdateOne(FM_OPL *OPL, int16_t *buffer, int length, int interleave);
+
+// Factory method
+FM_OPL *makeAdlibOPL(int rate);
+
+#endif
+
diff --git a/opl/ioperm_sys.c b/opl/ioperm_sys.c
new file mode 100644
index 00000000..8f50bcd3
--- /dev/null
+++ b/opl/ioperm_sys.c
@@ -0,0 +1,361 @@
+// Emacs style mode select   -*- C++ -*-
+//-----------------------------------------------------------------------------
+//
+// Copyright(C) 2002, 2003 Marcel Telka
+// Copyright(C) 2009 Simon Howard
+//
+// This program is free software; you can redistribute it and/or
+// modify it under the terms of the GNU General Public License
+// as published by the Free Software Foundation; either version 2
+// of the License, or (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with this program; if not, write to the Free Software
+// Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
+// 02111-1307, USA.
+//
+// DESCRIPTION:
+//     Interface to the ioperm.sys driver, based on code from the
+//     Cygwin ioperm library.
+//
+//-----------------------------------------------------------------------------
+
+#ifdef _WIN32
+
+#include <stdio.h>
+
+#define WIN32_LEAN_AND_MEAN
+#include <windows.h>
+#include <winioctl.h>
+
+#include <errno.h>
+
+#include "ioperm_sys.h"
+
+#define IOPERM_FILE L"\\\\.\\ioperm"
+
+#define IOCTL_IOPERM               \
+    CTL_CODE(FILE_DEVICE_UNKNOWN, 0xA00, METHOD_BUFFERED, FILE_ANY_ACCESS)
+
+struct ioperm_data
+{
+    unsigned long from;
+    unsigned long num;
+    int turn_on;
+};
+
+// Function pointers for advapi32.dll.  This DLL does not exist on
+// Windows 9x, so they are dynamically loaded from the DLL at runtime.
+
+static SC_HANDLE WINAPI (*MyOpenSCManagerW)(wchar_t *lpMachineName,
+                                            wchar_t *lpDatabaseName,
+                                            DWORD dwDesiredAccess) = NULL;
+static SC_HANDLE WINAPI (*MyCreateServiceW)(SC_HANDLE hSCManager,
+                                            wchar_t *lpServiceName,
+                                            wchar_t *lpDisplayName,
+                                            DWORD dwDesiredAccess,
+                                            DWORD dwServiceType,
+                                            DWORD dwStartType,
+                                            DWORD dwErrorControl,
+                                            wchar_t *lpBinaryPathName,
+                                            wchar_t *lpLoadOrderGroup,
+                                            LPDWORD lpdwTagId,
+                                            wchar_t *lpDependencies,
+                                            wchar_t *lpServiceStartName,
+                                            wchar_t *lpPassword);
+static SC_HANDLE WINAPI (*MyOpenServiceW)(SC_HANDLE hSCManager,
+                                          wchar_t *lpServiceName,
+                                          DWORD dwDesiredAccess);
+static BOOL WINAPI (*MyStartServiceW)(SC_HANDLE hService,
+                                      DWORD dwNumServiceArgs,
+                                      wchar_t **lpServiceArgVectors);
+static BOOL WINAPI (*MyControlService)(SC_HANDLE hService,
+                                       DWORD dwControl,
+                                       LPSERVICE_STATUS lpServiceStatus);
+static BOOL WINAPI (*MyCloseServiceHandle)(SC_HANDLE hSCObject);
+static BOOL WINAPI (*MyDeleteService)(SC_HANDLE hService);
+
+static struct
+{
+    char *name;
+    void **fn;
+} dll_functions[] = {
+    { "OpenSCManagerW",     (void **) &MyOpenSCManagerW },
+    { "CreateServiceW",     (void **) &MyCreateServiceW },
+    { "OpenServiceW",       (void **) &MyOpenServiceW },
+    { "StartServiceW",      (void **) &MyStartServiceW },
+    { "ControlService",     (void **) &MyControlService },
+    { "CloseServiceHandle", (void **) &MyCloseServiceHandle },
+    { "DeleteService",      (void **) &MyDeleteService },
+};
+
+// Globals
+
+static SC_HANDLE scm = NULL;
+static SC_HANDLE svc = NULL;
+static int service_was_created = 0;
+static int service_was_started = 0;
+
+static int LoadLibraryPointers(void)
+{
+    HMODULE dll;
+    int i;
+
+    // Already loaded?
+
+    if (MyOpenSCManagerW != NULL)
+    {
+        return 1;
+    }
+
+    dll = LoadLibraryW(L"advapi32.dll");
+
+    if (dll == NULL)
+    {
+        fprintf(stderr, "LoadLibraryPointers: Failed to open advapi32.dll\n");
+        return 0;
+    }
+
+    for (i = 0; i < sizeof(dll_functions) / sizeof(*dll_functions); ++i)
+    {
+        *dll_functions[i].fn = GetProcAddress(dll, dll_functions[i].name);
+
+        if (*dll_functions[i].fn == NULL)
+        {
+            fprintf(stderr, "LoadLibraryPointers: Failed to get address "
+                            "for '%s'\n", dll_functions[i].name);
+            return 0;
+        }
+    }
+
+    return 1;
+}
+
+int IOperm_EnablePortRange(unsigned int from, unsigned int num, int turn_on)
+{
+    HANDLE h;
+    struct ioperm_data ioperm_data;
+    DWORD BytesReturned;
+    BOOL r;
+
+    h = CreateFileW(IOPERM_FILE, GENERIC_READ, 0, NULL,
+                    OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, NULL);
+
+    if (h == INVALID_HANDLE_VALUE)
+    {
+        errno = ENODEV;
+        return -1;
+    }
+
+    ioperm_data.from = from;
+    ioperm_data.num = num;
+    ioperm_data.turn_on = turn_on;
+
+    r = DeviceIoControl(h, IOCTL_IOPERM,
+                        &ioperm_data, sizeof ioperm_data,
+                        NULL, 0,
+                        &BytesReturned, NULL);
+
+    if (!r)
+    {
+        errno = EPERM;
+    }
+
+    CloseHandle(h);
+
+    return r != 0;
+}
+
+// Load ioperm.sys driver.
+// Returns 1 for success, 0 for failure.
+// Remember to call IOperm_UninstallDriver to uninstall the driver later.
+
+int IOperm_InstallDriver(void)
+{
+    wchar_t driver_path[MAX_PATH];
+    int error;
+    int result = 1;
+
+    if (!LoadLibraryPointers())
+    {
+        return 0;
+    }
+
+    scm = MyOpenSCManagerW(NULL, NULL, SC_MANAGER_ALL_ACCESS);
+
+    if (scm == NULL)
+    {
+        error = GetLastError();
+        fprintf(stderr, "IOperm_InstallDriver: OpenSCManager failed (%i).\n",
+                        error);
+        return 0;
+    }
+
+    // Get the full path to the driver file.
+
+    GetFullPathNameW(L"ioperm.sys", MAX_PATH, driver_path, NULL);
+
+    // Create the service.
+
+    svc = MyCreateServiceW(scm,
+                           L"ioperm",
+                           L"ioperm support for Cygwin driver",
+                           SERVICE_ALL_ACCESS,
+                           SERVICE_KERNEL_DRIVER,
+                           SERVICE_AUTO_START,
+                           SERVICE_ERROR_NORMAL,
+                           driver_path,
+                           NULL,
+                           NULL,
+                           NULL,
+                           NULL,
+                           NULL);
+
+    if (svc == NULL)
+    {
+        error = GetLastError();
+
+        if (error != ERROR_SERVICE_EXISTS)
+        {
+            fprintf(stderr,
+                    "IOperm_InstallDriver: Failed to create service (%i).\n",
+                    error);
+        }
+        else
+        {
+            svc = MyOpenServiceW(scm, L"ioperm", SERVICE_ALL_ACCESS);
+
+            if (svc == NULL)
+            {
+                error = GetLastError();
+
+                fprintf(stderr,
+                        "IOperm_InstallDriver: Failed to open service (%i).\n",
+                        error);
+            }
+        }
+
+        if (svc == NULL)
+        {
+            MyCloseServiceHandle(scm);
+            return 0;
+        }
+    }
+    else
+    {
+        service_was_created = 1;
+    }
+
+    // Start the service.  If the service already existed, it might have
+    // already been running as well.
+
+    if (!MyStartServiceW(svc, 0, NULL))
+    {
+        error = GetLastError();
+
+        if (error != ERROR_SERVICE_ALREADY_RUNNING)
+        {
+            fprintf(stderr, "IOperm_InstallDriver: Failed to start service (%i).\n",
+                            error);
+
+            result = 0;
+        }
+        else
+        {
+            printf("IOperm_InstallDriver: ioperm driver already running.\n");
+        }
+    }
+    else
+    {
+        printf("IOperm_InstallDriver: ioperm driver installed.\n");
+        service_was_started = 1;
+    }
+
+    // If we failed to start the driver running, we need to clean up
+    // before finishing.
+
+    if (result == 0)
+    {
+        IOperm_UninstallDriver();
+    }
+
+    return result;
+}
+
+int IOperm_UninstallDriver(void)
+{
+    SERVICE_STATUS stat;
+    int result = 1;
+    int error;
+
+    // If we started the service, stop it.
+
+    if (service_was_started)
+    {
+        if (!MyControlService(svc, SERVICE_CONTROL_STOP, &stat))
+        {
+            error = GetLastError();
+
+            if (error == ERROR_SERVICE_NOT_ACTIVE)
+            {
+                fprintf(stderr,
+                        "IOperm_UninstallDriver: Service not active? (%i)\n",
+                        error);
+            }
+            else
+            {
+                fprintf(stderr,
+                        "IOperm_UninstallDriver: Failed to stop service (%i).\n",
+                        error);
+                result = 0;
+            }
+        }
+    }
+
+    // If we created the service, delete it.
+
+    if (service_was_created)
+    {
+        if (!MyDeleteService(svc))
+        {
+            error = GetLastError();
+
+            fprintf(stderr,
+                    "IOperm_UninstallDriver: DeleteService failed (%i).\n",
+                    error);
+
+            result = 0;
+        }
+        else if (service_was_started)
+        {
+            printf("IOperm_UnInstallDriver: ioperm driver uninstalled.\n");
+        }
+    }
+
+    // Close handles.
+
+    if (svc != NULL)
+    {
+        MyCloseServiceHandle(svc);
+        svc = NULL;
+    }
+
+    if (scm != NULL)
+    {
+        MyCloseServiceHandle(scm);
+        scm = NULL;
+    }
+
+    service_was_created = 0;
+    service_was_started = 0;
+
+    return result;
+}
+
+#endif /* #ifndef _WIN32 */
+
diff --git a/opl/ioperm_sys.h b/opl/ioperm_sys.h
new file mode 100644
index 00000000..faf17bf3
--- /dev/null
+++ b/opl/ioperm_sys.h
@@ -0,0 +1,36 @@
+// Emacs style mode select   -*- C++ -*-
+//-----------------------------------------------------------------------------
+//
+// Copyright(C) 2002, 2003 Marcel Telka
+// Copyright(C) 2009 Simon Howard
+//
+// This program is free software; you can redistribute it and/or
+// modify it under the terms of the GNU General Public License
+// as published by the Free Software Foundation; either version 2
+// of the License, or (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with this program; if not, write to the Free Software
+// Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
+// 02111-1307, USA.
+//
+// DESCRIPTION:
+//     Interface to the ioperm.sys driver, based on code from the
+//     Cygwin ioperm library.
+//
+//-----------------------------------------------------------------------------
+
+#ifndef IOPERM_SYS_H
+#define IOPERM_SYS_H
+
+int IOperm_EnablePortRange(unsigned int from, unsigned int num, int turn_on);
+int IOperm_InstallDriver(void);
+int IOperm_UninstallDriver(void);
+
+#endif /* #ifndef IOPERM_SYS_H */
+
diff --git a/opl/opl.c b/opl/opl.c
new file mode 100644
index 00000000..6d0e16db
--- /dev/null
+++ b/opl/opl.c
@@ -0,0 +1,466 @@
+// Emacs style mode select   -*- C++ -*-
+//-----------------------------------------------------------------------------
+//
+// Copyright(C) 2009 Simon Howard
+//
+// This program is free software; you can redistribute it and/or
+// modify it under the terms of the GNU General Public License
+// as published by the Free Software Foundation; either version 2
+// of the License, or (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with this program; if not, write to the Free Software
+// Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
+// 02111-1307, USA.
+//
+// DESCRIPTION:
+//     OPL interface.
+//
+//-----------------------------------------------------------------------------
+
+#include "config.h"
+
+#include <stdio.h>
+#include <stdlib.h>
+
+#ifdef _WIN32_WCE
+#include "libc_wince.h"
+#endif
+
+#include "SDL.h"
+
+#include "opl.h"
+#include "opl_internal.h"
+
+//#define OPL_DEBUG_TRACE
+
+#ifdef HAVE_IOPERM
+extern opl_driver_t opl_linux_driver;
+#endif
+#if defined(HAVE_LIBI386) || defined(HAVE_LIBAMD64)
+extern opl_driver_t opl_openbsd_driver;
+#endif
+#ifdef _WIN32
+extern opl_driver_t opl_win32_driver;
+#endif
+extern opl_driver_t opl_sdl_driver;
+
+static opl_driver_t *drivers[] =
+{
+#ifdef HAVE_IOPERM
+    &opl_linux_driver,
+#endif
+#if defined(HAVE_LIBI386) || defined(HAVE_LIBAMD64)
+    &opl_openbsd_driver,
+#endif
+#ifdef _WIN32
+    &opl_win32_driver,
+#endif
+    &opl_sdl_driver,
+    NULL
+};
+
+static opl_driver_t *driver = NULL;
+static int init_stage_reg_writes = 1;
+
+unsigned int opl_sample_rate = 22050;
+
+//
+// Init/shutdown code.
+//
+
+// Initialize the specified driver and detect an OPL chip.  Returns
+// true if an OPL is detected.
+
+static int InitDriver(opl_driver_t *_driver, unsigned int port_base)
+{
+    // Initialize the driver.
+
+    if (!_driver->init_func(port_base))
+    {
+        return 0;
+    }
+
+    // The driver was initialized okay, so we now have somewhere
+    // to write to.  It doesn't mean there's an OPL chip there,
+    // though.  Perform the detection sequence to make sure.
+    // (it's done twice, like how Doom does it).
+
+    driver = _driver;
+    init_stage_reg_writes = 1;
+
+    if (!OPL_Detect() || !OPL_Detect())
+    {
+        printf("OPL_Init: No OPL detected using '%s' driver.\n", _driver->name);
+        _driver->shutdown_func();
+        driver = NULL;
+        return 0;
+    }
+
+    // Initialize all registers.
+
+    OPL_InitRegisters();
+
+    init_stage_reg_writes = 0;
+
+    printf("OPL_Init: Using driver '%s'.\n", driver->name);
+
+    return 1;
+}
+
+// Find a driver automatically by trying each in the list.
+
+static int AutoSelectDriver(unsigned int port_base)
+{
+    int i;
+
+    for (i=0; drivers[i] != NULL; ++i)
+    {
+        if (InitDriver(drivers[i], port_base))
+        {
+            return 1;
+        }
+    }
+
+    printf("OPL_Init: Failed to find a working driver.\n");
+
+    return 0;
+}
+
+// Initialize the OPL library.  Returns true if initialized
+// successfully.
+
+int OPL_Init(unsigned int port_base)
+{
+    char *driver_name;
+    int i;
+
+    driver_name = getenv("OPL_DRIVER");
+
+    if (driver_name != NULL)
+    {
+        // Search the list until we find the driver with this name.
+
+        for (i=0; drivers[i] != NULL; ++i)
+        {
+            if (!strcmp(driver_name, drivers[i]->name))
+            {
+                if (InitDriver(drivers[i], port_base))
+                {
+                    return 1;
+                }
+                else
+                {
+                    printf("OPL_Init: Failed to initialize "
+                           "driver: '%s'.\n", driver_name);
+                    return 0;
+                }
+            }
+        }
+
+        printf("OPL_Init: unknown driver: '%s'.\n", driver_name);
+
+        return 0;
+    }
+    else
+    {
+        return AutoSelectDriver(port_base);
+    }
+}
+
+// Shut down the OPL library.
+
+void OPL_Shutdown(void)
+{
+    if (driver != NULL)
+    {
+        driver->shutdown_func();
+        driver = NULL;
+    }
+}
+
+// Set the sample rate used for software OPL emulation.
+
+void OPL_SetSampleRate(unsigned int rate)
+{
+    opl_sample_rate = rate;
+}
+
+void OPL_WritePort(opl_port_t port, unsigned int value)
+{
+    if (driver != NULL)
+    {
+#ifdef OPL_DEBUG_TRACE
+        printf("OPL_write: %i, %x\n", port, value);
+        fflush(stdout);
+#endif
+        driver->write_port_func(port, value);
+    }
+}
+
+unsigned int OPL_ReadPort(opl_port_t port)
+{
+    if (driver != NULL)
+    {
+        unsigned int result;
+
+#ifdef OPL_DEBUG_TRACE
+        printf("OPL_read: %i...\n", port);
+        fflush(stdout);
+#endif
+
+        result = driver->read_port_func(port);
+
+#ifdef OPL_DEBUG_TRACE
+        printf("OPL_read: %i -> %x\n", port, result);
+        fflush(stdout);
+#endif
+
+        return result;
+    }
+    else
+    {
+        return 0;
+    }
+}
+
+//
+// Higher-level functions, based on the lower-level functions above
+// (register write, etc).
+//
+
+unsigned int OPL_ReadStatus(void)
+{
+    return OPL_ReadPort(OPL_REGISTER_PORT);
+}
+
+// Write an OPL register value
+
+void OPL_WriteRegister(int reg, int value)
+{
+    int i;
+
+    OPL_WritePort(OPL_REGISTER_PORT, reg);
+
+    // For timing, read the register port six times after writing the
+    // register number to cause the appropriate delay
+
+    for (i=0; i<6; ++i)
+    {
+        // An oddity of the Doom OPL code: at startup initialization,
+        // the spacing here is performed by reading from the register
+        // port; after initialization, the data port is read, instead.
+
+        if (init_stage_reg_writes)
+        {
+            OPL_ReadPort(OPL_REGISTER_PORT);
+        }
+        else
+        {
+            OPL_ReadPort(OPL_DATA_PORT);
+        }
+    }
+
+    OPL_WritePort(OPL_DATA_PORT, value);
+
+    // Read the register port 24 times after writing the value to
+    // cause the appropriate delay
+
+    for (i=0; i<24; ++i)
+    {
+        OPL_ReadStatus();
+    }
+}
+
+// Detect the presence of an OPL chip
+
+int OPL_Detect(void)
+{
+    int result1, result2;
+    int i;
+
+    // Reset both timers:
+    OPL_WriteRegister(OPL_REG_TIMER_CTRL, 0x60);
+
+    // Enable interrupts:
+    OPL_WriteRegister(OPL_REG_TIMER_CTRL, 0x80);
+
+    // Read status
+    result1 = OPL_ReadStatus();
+
+    // Set timer:
+    OPL_WriteRegister(OPL_REG_TIMER1, 0xff);
+
+    // Start timer 1:
+    OPL_WriteRegister(OPL_REG_TIMER_CTRL, 0x21);
+
+    // Wait for 80 microseconds
+    // This is how Doom does it:
+
+    for (i=0; i<200; ++i)
+    {
+        OPL_ReadStatus();
+    }
+
+    OPL_Delay(1);
+
+    // Read status
+    result2 = OPL_ReadStatus();
+
+    // Reset both timers:
+    OPL_WriteRegister(OPL_REG_TIMER_CTRL, 0x60);
+
+    // Enable interrupts:
+    OPL_WriteRegister(OPL_REG_TIMER_CTRL, 0x80);
+
+    return (result1 & 0xe0) == 0x00
+        && (result2 & 0xe0) == 0xc0;
+}
+
+// Initialize registers on startup
+
+void OPL_InitRegisters(void)
+{
+    int r;
+
+    // Initialize level registers
+
+    for (r=OPL_REGS_LEVEL; r <= OPL_REGS_LEVEL + OPL_NUM_OPERATORS; ++r)
+    {
+        OPL_WriteRegister(r, 0x3f);
+    }
+
+    // Initialize other registers
+    // These two loops write to registers that actually don't exist,
+    // but this is what Doom does ...
+    // Similarly, the <= is also intenational.
+
+    for (r=OPL_REGS_ATTACK; r <= OPL_REGS_WAVEFORM + OPL_NUM_OPERATORS; ++r)
+    {
+        OPL_WriteRegister(r, 0x00);
+    }
+
+    // More registers ...
+
+    for (r=1; r < OPL_REGS_LEVEL; ++r)
+    {
+        OPL_WriteRegister(r, 0x00);
+    }
+
+    // Re-initialize the low registers:
+
+    // Reset both timers and enable interrupts:
+    OPL_WriteRegister(OPL_REG_TIMER_CTRL,      0x60);
+    OPL_WriteRegister(OPL_REG_TIMER_CTRL,      0x80);
+
+    // "Allow FM chips to control the waveform of each operator":
+    OPL_WriteRegister(OPL_REG_WAVEFORM_ENABLE, 0x20);
+
+    // Keyboard split point on (?)
+    OPL_WriteRegister(OPL_REG_FM_MODE,         0x40);
+}
+
+//
+// Timer functions.
+//
+
+void OPL_SetCallback(unsigned int ms, opl_callback_t callback, void *data)
+{
+    if (driver != NULL)
+    {
+        driver->set_callback_func(ms, callback, data);
+    }
+}
+
+void OPL_ClearCallbacks(void)
+{
+    if (driver != NULL)
+    {
+        driver->clear_callbacks_func();
+    }
+}
+
+void OPL_Lock(void)
+{
+    if (driver != NULL)
+    {
+        driver->lock_func();
+    }
+}
+
+void OPL_Unlock(void)
+{
+    if (driver != NULL)
+    {
+        driver->unlock_func();
+    }
+}
+
+typedef struct
+{
+    int finished;
+
+    SDL_mutex *mutex;
+    SDL_cond *cond;
+} delay_data_t;
+
+static void DelayCallback(void *_delay_data)
+{
+    delay_data_t *delay_data = _delay_data;
+
+    SDL_LockMutex(delay_data->mutex);
+    delay_data->finished = 1;
+
+    SDL_CondSignal(delay_data->cond);
+
+    SDL_UnlockMutex(delay_data->mutex);
+}
+
+void OPL_Delay(unsigned int ms)
+{
+    delay_data_t delay_data;
+
+    if (driver == NULL)
+    {
+        return;
+    }
+
+    // Create a callback that will signal this thread after the
+    // specified time.
+
+    delay_data.finished = 0;
+    delay_data.mutex = SDL_CreateMutex();
+    delay_data.cond = SDL_CreateCond();
+
+    OPL_SetCallback(ms, DelayCallback, &delay_data);
+
+    // Wait until the callback is invoked.
+
+    SDL_LockMutex(delay_data.mutex);
+
+    while (!delay_data.finished)
+    {
+        SDL_CondWait(delay_data.cond, delay_data.mutex);
+    }
+
+    SDL_UnlockMutex(delay_data.mutex);
+
+    // Clean up.
+
+    SDL_DestroyMutex(delay_data.mutex);
+    SDL_DestroyCond(delay_data.cond);
+}
+
+void OPL_SetPaused(int paused)
+{
+    if (driver != NULL)
+    {
+        driver->set_paused_func(paused);
+    }
+}
+
diff --git a/opl/opl.h b/opl/opl.h
new file mode 100644
index 00000000..04d3cf27
--- /dev/null
+++ b/opl/opl.h
@@ -0,0 +1,137 @@
+// Emacs style mode select   -*- C++ -*- 
+//-----------------------------------------------------------------------------
+//
+// Copyright(C) 2009 Simon Howard
+//
+// This program is free software; you can redistribute it and/or
+// modify it under the terms of the GNU General Public License
+// as published by the Free Software Foundation; either version 2
+// of the License, or (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with this program; if not, write to the Free Software
+// Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
+// 02111-1307, USA.
+//
+// DESCRIPTION:
+//     OPL interface.
+//
+//-----------------------------------------------------------------------------
+
+
+#ifndef OPL_OPL_H
+#define OPL_OPL_H
+
+typedef void (*opl_callback_t)(void *data);
+
+typedef enum
+{
+    OPL_REGISTER_PORT = 0,
+    OPL_DATA_PORT = 1
+} opl_port_t;
+
+#define OPL_NUM_OPERATORS   21
+#define OPL_NUM_VOICES      9
+
+#define OPL_REG_WAVEFORM_ENABLE   0x01
+#define OPL_REG_TIMER1            0x02
+#define OPL_REG_TIMER2            0x03
+#define OPL_REG_TIMER_CTRL        0x04
+#define OPL_REG_FM_MODE           0x08
+
+// Operator registers (21 of each):
+
+#define OPL_REGS_TREMOLO          0x20
+#define OPL_REGS_LEVEL            0x40
+#define OPL_REGS_ATTACK           0x60
+#define OPL_REGS_SUSTAIN          0x80
+#define OPL_REGS_WAVEFORM         0xE0
+
+// Voice registers (9 of each):
+
+#define OPL_REGS_FREQ_1           0xA0
+#define OPL_REGS_FREQ_2           0xB0
+#define OPL_REGS_FEEDBACK         0xC0
+
+//
+// Low-level functions.
+//
+
+// Initialize the OPL subsystem.
+
+int OPL_Init(unsigned int port_base);
+
+// Shut down the OPL subsystem.
+
+void OPL_Shutdown(void);
+
+// Set the sample rate used for software emulation.
+
+void OPL_SetSampleRate(unsigned int rate);
+
+// Write to one of the OPL I/O ports:
+
+void OPL_WritePort(opl_port_t port, unsigned int value);
+
+// Read from one of the OPL I/O ports:
+
+unsigned int OPL_ReadPort(opl_port_t port);
+
+//
+// Higher-level functions.
+//
+
+// Read the cuurrent status byte of the OPL chip.
+
+unsigned int OPL_ReadStatus(void);
+
+// Write to an OPL register.
+
+void OPL_WriteRegister(int reg, int value);
+
+// Perform a detection sequence to determine that an
+// OPL chip is present.
+
+int OPL_Detect(void);
+
+// Initialize all registers, performed on startup.
+
+void OPL_InitRegisters(void);
+
+//
+// Timer callback functions.
+//
+
+// Set a timer callback.  After the specified number of milliseconds
+// have elapsed, the callback will be invoked.
+
+void OPL_SetCallback(unsigned int ms, opl_callback_t callback, void *data);
+
+// Clear all OPL callbacks that have been set.
+
+void OPL_ClearCallbacks(void);
+
+// Begin critical section, during which, OPL callbacks will not be
+// invoked.
+
+void OPL_Lock(void);
+
+// End critical section.
+
+void OPL_Unlock(void);
+
+// Block until the specified number of milliseconds have elapsed.
+
+void OPL_Delay(unsigned int ms);
+
+// Pause the OPL callbacks.
+
+void OPL_SetPaused(int paused);
+
+#endif
+
diff --git a/opl/opl_internal.h b/opl/opl_internal.h
new file mode 100644
index 00000000..4a46b060
--- /dev/null
+++ b/opl/opl_internal.h
@@ -0,0 +1,64 @@
+// Emacs style mode select   -*- C++ -*- 
+//-----------------------------------------------------------------------------
+//
+// Copyright(C) 2009 Simon Howard
+//
+// This program is free software; you can redistribute it and/or
+// modify it under the terms of the GNU General Public License
+// as published by the Free Software Foundation; either version 2
+// of the License, or (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with this program; if not, write to the Free Software
+// Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
+// 02111-1307, USA.
+//
+// DESCRIPTION:
+//     OPL internal interface.
+//
+//-----------------------------------------------------------------------------
+
+
+#ifndef OPL_INTERNAL_H
+#define OPL_INTERNAL_H
+
+#include "opl.h"
+
+typedef int (*opl_init_func)(unsigned int port_base);
+typedef void (*opl_shutdown_func)(void);
+typedef unsigned int (*opl_read_port_func)(opl_port_t port);
+typedef void (*opl_write_port_func)(opl_port_t port, unsigned int value);
+typedef void (*opl_set_callback_func)(unsigned int ms,
+                                      opl_callback_t callback,
+                                      void *data);
+typedef void (*opl_clear_callbacks_func)(void);
+typedef void (*opl_lock_func)(void);
+typedef void (*opl_unlock_func)(void);
+typedef void (*opl_set_paused_func)(int paused);
+
+typedef struct
+{
+    char *name;
+
+    opl_init_func init_func;
+    opl_shutdown_func shutdown_func;
+    opl_read_port_func read_port_func;
+    opl_write_port_func write_port_func;
+    opl_set_callback_func set_callback_func;
+    opl_clear_callbacks_func clear_callbacks_func;
+    opl_lock_func lock_func;
+    opl_unlock_func unlock_func;
+    opl_set_paused_func set_paused_func;
+} opl_driver_t;
+
+// Sample rate to use when doing software emulation.
+
+extern unsigned int opl_sample_rate;
+
+#endif /* #ifndef OPL_INTERNAL_H */
+
diff --git a/opl/opl_linux.c b/opl/opl_linux.c
new file mode 100644
index 00000000..319686b8
--- /dev/null
+++ b/opl/opl_linux.c
@@ -0,0 +1,110 @@
+// Emacs style mode select   -*- C++ -*- 
+//-----------------------------------------------------------------------------
+//
+// Copyright(C) 2009 Simon Howard
+//
+// This program is free software; you can redistribute it and/or
+// modify it under the terms of the GNU General Public License
+// as published by the Free Software Foundation; either version 2
+// of the License, or (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with this program; if not, write to the Free Software
+// Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
+// 02111-1307, USA.
+//
+// DESCRIPTION:
+//     OPL Linux interface.
+//
+//-----------------------------------------------------------------------------
+
+#include "config.h"
+
+#ifdef HAVE_IOPERM
+
+#include <stdio.h>
+#include <string.h>
+#include <errno.h>
+#include <unistd.h>
+#include <sys/io.h>
+
+#include "opl.h"
+#include "opl_internal.h"
+#include "opl_timer.h"
+
+static unsigned int opl_port_base;
+
+static int OPL_Linux_Init(unsigned int port_base)
+{
+    // Try to get permissions:
+
+    if (ioperm(port_base, 2, 1) < 0)
+    {
+        fprintf(stderr, "Failed to get I/O port permissions for 0x%x: %s\n",
+                        port_base, strerror(errno));
+
+        if (errno == EPERM)
+        {
+            fprintf(stderr,
+                    "\tYou may need to run the program as root in order\n"
+                    "\tto acquire I/O port permissions for OPL MIDI playback.\n");
+        }
+
+        return 0;
+    }
+
+    opl_port_base = port_base;
+
+    // Start callback thread
+
+    if (!OPL_Timer_StartThread())
+    {
+        ioperm(port_base, 2, 0);
+        return 0;
+    }
+
+    return 1;
+}
+
+static void OPL_Linux_Shutdown(void)
+{
+    // Stop callback thread
+
+    OPL_Timer_StopThread();
+
+    // Release permissions
+
+    ioperm(opl_port_base, 2, 0);
+}
+
+static unsigned int OPL_Linux_PortRead(opl_port_t port)
+{
+    return inb(opl_port_base + port);
+}
+
+static void OPL_Linux_PortWrite(opl_port_t port, unsigned int value)
+{
+    outb(value, opl_port_base + port);
+}
+
+opl_driver_t opl_linux_driver =
+{
+    "Linux",
+    OPL_Linux_Init,
+    OPL_Linux_Shutdown,
+    OPL_Linux_PortRead,
+    OPL_Linux_PortWrite,
+    OPL_Timer_SetCallback,
+    OPL_Timer_ClearCallbacks,
+    OPL_Timer_Lock,
+    OPL_Timer_Unlock,
+    OPL_Timer_SetPaused
+};
+
+#endif /* #ifdef HAVE_IOPERM */
+
diff --git a/opl/opl_obsd.c b/opl/opl_obsd.c
new file mode 100644
index 00000000..b07a0421
--- /dev/null
+++ b/opl/opl_obsd.c
@@ -0,0 +1,125 @@
+// Emacs style mode select   -*- C++ -*- 
+//-----------------------------------------------------------------------------
+//
+// Copyright(C) 2009 Simon Howard
+//
+// This program is free software; you can redistribute it and/or
+// modify it under the terms of the GNU General Public License
+// as published by the Free Software Foundation; either version 2
+// of the License, or (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with this program; if not, write to the Free Software
+// Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
+// 02111-1307, USA.
+//
+// DESCRIPTION:
+//     OPL OpenBSD interface (also NetBSD)
+//
+//-----------------------------------------------------------------------------
+
+#include "config.h"
+
+// OpenBSD has a i386_iopl on i386 and amd64_iopl on x86_64,
+// even though they do the same thing.  Take care of this
+// here, and map set_iopl to point to the appropriate name.
+
+#if defined(HAVE_LIBI386)
+
+#include <sys/types.h>
+#include <machine/sysarch.h>
+#include <i386/pio.h>
+#define set_iopl i386_iopl
+
+#elif defined(HAVE_LIBAMD64)
+
+#include <sys/types.h>
+#include <machine/sysarch.h>
+#include <amd64/pio.h>
+#define set_iopl amd64_iopl
+
+#else
+#define NO_OBSD_DRIVER
+#endif
+
+// If the above succeeded, proceed with the rest.
+
+#ifndef NO_OBSD_DRIVER
+
+#include <stdio.h>
+#include <string.h>
+#include <errno.h>
+#include <unistd.h>
+
+#include "opl.h"
+#include "opl_internal.h"
+#include "opl_timer.h"
+
+static unsigned int opl_port_base;
+
+static int OPL_OpenBSD_Init(unsigned int port_base)
+{
+    // Try to get permissions:
+
+    if (set_iopl(3) < 0)
+    {
+        fprintf(stderr, "Failed to get raise I/O privilege level: "
+                        "check that you are running as root.\n");
+        return 0;
+    }
+
+    opl_port_base = port_base;
+
+    // Start callback thread
+
+    if (!OPL_Timer_StartThread())
+    {
+        set_iopl(0);
+        return 0;
+    }
+
+    return 1;
+}
+
+static void OPL_OpenBSD_Shutdown(void)
+{
+    // Stop callback thread
+
+    OPL_Timer_StopThread();
+
+    // Release I/O port permissions:
+
+    set_iopl(0);
+}
+
+static unsigned int OPL_OpenBSD_PortRead(opl_port_t port)
+{
+    return inb(opl_port_base + port);
+}
+
+static void OPL_OpenBSD_PortWrite(opl_port_t port, unsigned int value)
+{
+    outb(opl_port_base + port, value);
+}
+
+opl_driver_t opl_openbsd_driver =
+{
+    "OpenBSD",
+    OPL_OpenBSD_Init,
+    OPL_OpenBSD_Shutdown,
+    OPL_OpenBSD_PortRead,
+    OPL_OpenBSD_PortWrite,
+    OPL_Timer_SetCallback,
+    OPL_Timer_ClearCallbacks,
+    OPL_Timer_Lock,
+    OPL_Timer_Unlock,
+    OPL_Timer_SetPaused
+};
+
+#endif /* #ifndef NO_OBSD_DRIVER */
+
diff --git a/opl/opl_queue.c b/opl/opl_queue.c
new file mode 100644
index 00000000..f9d4c377
--- /dev/null
+++ b/opl/opl_queue.c
@@ -0,0 +1,280 @@
+// Emacs style mode select   -*- C++ -*- 
+//-----------------------------------------------------------------------------
+//
+// Copyright(C) 2009 Simon Howard
+//
+// This program is free software; you can redistribute it and/or
+// modify it under the terms of the GNU General Public License
+// as published by the Free Software Foundation; either version 2
+// of the License, or (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with this program; if not, write to the Free Software
+// Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
+// 02111-1307, USA.
+//
+// DESCRIPTION:
+//     Queue of waiting callbacks, stored in a binary min heap, so that we
+//     can always get the first callback.
+//
+//-----------------------------------------------------------------------------
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include "opl_queue.h"
+
+#define MAX_OPL_QUEUE 64
+
+typedef struct
+{
+    opl_callback_t callback;
+    void *data;
+    unsigned int time;
+} opl_queue_entry_t;
+
+struct opl_callback_queue_s
+{
+    opl_queue_entry_t entries[MAX_OPL_QUEUE];
+    unsigned int num_entries;
+};
+
+opl_callback_queue_t *OPL_Queue_Create(void)
+{
+    opl_callback_queue_t *queue;
+
+    queue = malloc(sizeof(opl_callback_queue_t));
+    queue->num_entries = 0;
+
+    return queue;
+}
+
+void OPL_Queue_Destroy(opl_callback_queue_t *queue)
+{
+    free(queue);
+}
+
+int OPL_Queue_IsEmpty(opl_callback_queue_t *queue)
+{
+    return queue->num_entries == 0;
+}
+
+void OPL_Queue_Clear(opl_callback_queue_t *queue)
+{
+    queue->num_entries = 0;
+}
+
+void OPL_Queue_Push(opl_callback_queue_t *queue,
+                    opl_callback_t callback, void *data,
+                    unsigned int time)
+{
+    int entry_id;
+    int parent_id;
+
+    if (queue->num_entries >= MAX_OPL_QUEUE)
+    {
+        fprintf(stderr, "OPL_Queue_Push: Exceeded maximum callbacks\n");
+        return;
+    }
+
+    // Add to last queue entry.
+
+    entry_id = queue->num_entries;
+    ++queue->num_entries;
+
+    // Shift existing entries down in the heap.
+
+    while (entry_id > 0)
+    {
+        parent_id = (entry_id - 1) / 2;
+
+        // Is the heap condition satisfied?
+
+        if (time >= queue->entries[parent_id].time)
+        {
+            break;
+        }
+
+        // Move the existing entry down in the heap.
+
+        memcpy(&queue->entries[entry_id],
+               &queue->entries[parent_id],
+               sizeof(opl_queue_entry_t));
+
+        // Advance to the parent.
+
+        entry_id = parent_id;
+    }
+
+    // Insert new callback data.
+
+    queue->entries[entry_id].callback = callback;
+    queue->entries[entry_id].data = data;
+    queue->entries[entry_id].time = time;
+}
+
+int OPL_Queue_Pop(opl_callback_queue_t *queue,
+                  opl_callback_t *callback, void **data)
+{
+    opl_queue_entry_t *entry;
+    int child1, child2;
+    int i, next_i;
+
+    // Empty?
+
+    if (queue->num_entries <= 0)
+    {
+        return 0;
+    }
+
+    // Store the result:
+
+    *callback = queue->entries[0].callback;
+    *data = queue->entries[0].data;
+
+    // Decrease the heap size, and keep pointer to the last entry in
+    // the heap, which must now be percolated down from the top.
+
+    --queue->num_entries;
+    entry = &queue->entries[queue->num_entries];
+
+    // Percolate down.
+
+    i = 0;
+
+    for (;;)
+    {
+        child1 = i * 2 + 1;
+        child2 = i * 2 + 2;
+
+        if (child1 < queue->num_entries
+         && queue->entries[child1].time < entry->time)
+        {
+            // Left child is less than entry.
+            // Use the minimum of left and right children.
+
+            if (child2 < queue->num_entries
+             && queue->entries[child2].time < queue->entries[child1].time)
+            {
+                next_i = child2;
+            }
+            else
+            {
+                next_i = child1;
+            }
+        }
+        else if (child2 < queue->num_entries
+              && queue->entries[child2].time < entry->time)
+        {
+            // Right child is less than entry.  Go down the right side.
+
+            next_i = child2;
+        }
+        else
+        {
+            // Finished percolating.
+            break;
+        }
+
+        // Percolate the next value up and advance.
+
+        memcpy(&queue->entries[i],
+               &queue->entries[next_i],
+               sizeof(opl_queue_entry_t));
+        i = next_i;
+    }
+
+    // Store the old last-entry at its new position.
+
+    memcpy(&queue->entries[i], entry, sizeof(opl_queue_entry_t));
+
+    return 1;
+}
+
+unsigned int OPL_Queue_Peek(opl_callback_queue_t *queue)
+{
+    if (queue->num_entries > 0)
+    {
+        return queue->entries[0].time;
+    }
+    else
+    {
+        return 0;
+    }
+}
+
+#ifdef TEST
+
+#include <assert.h>
+
+static void PrintQueueNode(opl_callback_queue_t *queue, int node, int depth)
+{
+    int i;
+
+    if (node >= queue->num_entries)
+    {
+        return;
+    }
+
+    for (i=0; i<depth * 3; ++i)
+    {
+        printf(" ");
+    }
+
+    printf("%i\n", queue->entries[node].time);
+
+    PrintQueueNode(queue, node * 2 + 1, depth + 1);
+    PrintQueueNode(queue, node * 2 + 2, depth + 1);
+}
+
+static void PrintQueue(opl_callback_queue_t *queue)
+{
+    PrintQueueNode(queue, 0, 0);
+}
+
+int main()
+{
+    opl_callback_queue_t *queue;
+    int iteration;
+
+    queue = OPL_Queue_Create();
+
+    for (iteration=0; iteration<5000; ++iteration)
+    {
+        opl_callback_t callback;
+        void *data;
+        unsigned int time;
+        unsigned int newtime;
+        int i;
+
+        for (i=0; i<MAX_OPL_QUEUE; ++i)
+        {
+            time = rand() % 0x10000;
+            OPL_Queue_Push(queue, NULL, NULL, time);
+        }
+
+        time = 0;
+
+        for (i=0; i<MAX_OPL_QUEUE; ++i)
+        {
+            assert(!OPL_Queue_IsEmpty(queue));
+            newtime = OPL_Queue_Peek(queue);
+            assert(OPL_Queue_Pop(queue, &callback, &data));
+
+            assert(newtime >= time);
+            time = newtime;
+        }
+
+        assert(OPL_Queue_IsEmpty(queue));
+        assert(!OPL_Queue_Pop(queue, &callback, &data));
+    }
+}
+
+#endif
+
diff --git a/opl/opl_queue.h b/opl/opl_queue.h
new file mode 100644
index 00000000..2447702b
--- /dev/null
+++ b/opl/opl_queue.h
@@ -0,0 +1,45 @@
+// Emacs style mode select   -*- C++ -*- 
+//-----------------------------------------------------------------------------
+//
+// Copyright(C) 2009 Simon Howard
+//
+// This program is free software; you can redistribute it and/or
+// modify it under the terms of the GNU General Public License
+// as published by the Free Software Foundation; either version 2
+// of the License, or (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with this program; if not, write to the Free Software
+// Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
+// 02111-1307, USA.
+//
+// DESCRIPTION:
+//     OPL callback queue.
+//
+//-----------------------------------------------------------------------------
+
+#ifndef OPL_QUEUE_H
+#define OPL_QUEUE_H
+
+#include "opl.h"
+
+typedef struct opl_callback_queue_s opl_callback_queue_t;
+
+opl_callback_queue_t *OPL_Queue_Create(void);
+int OPL_Queue_IsEmpty(opl_callback_queue_t *queue);
+void OPL_Queue_Clear(opl_callback_queue_t *queue);
+void OPL_Queue_Destroy(opl_callback_queue_t *queue);
+void OPL_Queue_Push(opl_callback_queue_t *queue,
+                    opl_callback_t callback, void *data,
+                    unsigned int time);
+int OPL_Queue_Pop(opl_callback_queue_t *queue,
+                  opl_callback_t *callback, void **data);
+unsigned int OPL_Queue_Peek(opl_callback_queue_t *queue);
+
+#endif /* #ifndef OPL_QUEUE_H */
+
diff --git a/opl/opl_sdl.c b/opl/opl_sdl.c
new file mode 100644
index 00000000..1963d5cd
--- /dev/null
+++ b/opl/opl_sdl.c
@@ -0,0 +1,452 @@
+// Emacs style mode select   -*- C++ -*- 
+//-----------------------------------------------------------------------------
+//
+// Copyright(C) 2009 Simon Howard
+//
+// This program is free software; you can redistribute it and/or
+// modify it under the terms of the GNU General Public License
+// as published by the Free Software Foundation; either version 2
+// of the License, or (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with this program; if not, write to the Free Software
+// Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
+// 02111-1307, USA.
+//
+// DESCRIPTION:
+//     OPL SDL interface.
+//
+//-----------------------------------------------------------------------------
+
+#include "config.h"
+
+#include <stdio.h>
+#include <string.h>
+#include <errno.h>
+#include <assert.h>
+
+#include "SDL.h"
+#include "SDL_mixer.h"
+
+#include "fmopl.h"
+
+#include "opl.h"
+#include "opl_internal.h"
+
+#include "opl_queue.h"
+
+#define MAX_SOUND_SLICE_TIME 100 /* ms */
+
+// When the callback mutex is locked using OPL_Lock, callback functions
+// are not invoked.
+
+static SDL_mutex *callback_mutex = NULL;
+
+// Queue of callbacks waiting to be invoked.
+
+static opl_callback_queue_t *callback_queue;
+
+// Mutex used to control access to the callback queue.
+
+static SDL_mutex *callback_queue_mutex = NULL;
+
+// Current time, in number of samples since startup:
+
+static int current_time;
+
+// If non-zero, playback is currently paused.
+
+static int opl_sdl_paused;
+
+// Time offset (in samples) due to the fact that callbacks
+// were previously paused.
+
+static unsigned int pause_offset;
+
+// OPL software emulator structure.
+
+static FM_OPL *opl_emulator = NULL;
+
+// Temporary mixing buffer used by the mixing callback.
+
+static int16_t *mix_buffer = NULL;
+
+// SDL parameters.
+
+static int sdl_was_initialized = 0;
+static int mixing_freq, mixing_channels;
+static Uint16 mixing_format;
+
+static int SDLIsInitialized(void)
+{
+    int freq, channels;
+    Uint16 format;
+
+    return Mix_QuerySpec(&freq, &format, &channels);
+}
+
+// Advance time by the specified number of samples, invoking any
+// callback functions as appropriate.
+
+static void AdvanceTime(unsigned int nsamples)
+{
+    opl_callback_t callback;
+    void *callback_data;
+
+    SDL_LockMutex(callback_queue_mutex);
+
+    // Advance time.
+
+    current_time += nsamples;
+
+    if (opl_sdl_paused)
+    {
+        pause_offset += nsamples;
+    }
+
+    // Are there callbacks to invoke now?  Keep invoking them
+    // until there are none more left.
+
+    while (!OPL_Queue_IsEmpty(callback_queue)
+        && current_time >= OPL_Queue_Peek(callback_queue) + pause_offset)
+    {
+        // Pop the callback from the queue to invoke it.
+
+        if (!OPL_Queue_Pop(callback_queue, &callback, &callback_data))
+        {
+            break;
+        }
+
+        // The mutex stuff here is a bit complicated.  We must
+        // hold callback_mutex when we invoke the callback (so that
+        // the control thread can use OPL_Lock() to prevent callbacks
+        // from being invoked), but we must not be holding
+        // callback_queue_mutex, as the callback must be able to
+        // call OPL_SetCallback to schedule new callbacks.
+
+        SDL_UnlockMutex(callback_queue_mutex);
+
+        SDL_LockMutex(callback_mutex);
+        callback(callback_data);
+        SDL_UnlockMutex(callback_mutex);
+
+        SDL_LockMutex(callback_queue_mutex);
+    }
+
+    SDL_UnlockMutex(callback_queue_mutex);
+}
+
+// Call the OPL emulator code to fill the specified buffer.
+
+static void FillBuffer(int16_t *buffer, unsigned int nsamples)
+{
+    unsigned int i;
+
+    // This seems like a reasonable assumption.  mix_buffer is
+    // 1 second long, which should always be much longer than the
+    // SDL mix buffer.
+
+    assert(nsamples < mixing_freq);
+
+    YM3812UpdateOne(opl_emulator, mix_buffer, nsamples, 0);
+
+    // Mix into the destination buffer, doubling up into stereo.
+
+    for (i=0; i<nsamples; ++i)
+    {
+        buffer[i * 2] = mix_buffer[i];
+        buffer[i * 2 + 1] = mix_buffer[i];
+    }
+}
+
+// Callback function to fill a new sound buffer:
+
+static void OPL_Mix_Callback(void *udata,
+                             Uint8 *byte_buffer,
+                             int buffer_bytes)
+{
+    int16_t *buffer;
+    unsigned int buffer_len;
+    unsigned int filled = 0;
+
+    // Buffer length in samples (quadrupled, because of 16-bit and stereo)
+
+    buffer = (int16_t *) byte_buffer;
+    buffer_len = buffer_bytes / 4;
+
+    // Repeatedly call the FMOPL update function until the buffer is
+    // full.
+
+    while (filled < buffer_len)
+    {
+        unsigned int next_callback_time;
+        unsigned int nsamples;
+
+        SDL_LockMutex(callback_queue_mutex);
+
+        // Work out the time until the next callback waiting in
+        // the callback queue must be invoked.  We can then fill the
+        // buffer with this many samples.
+
+        if (opl_sdl_paused || OPL_Queue_IsEmpty(callback_queue))
+        {
+            nsamples = buffer_len - filled;
+        }
+        else
+        {
+            next_callback_time = OPL_Queue_Peek(callback_queue) + pause_offset;
+
+            nsamples = next_callback_time - current_time;
+
+            if (nsamples > buffer_len - filled)
+            {
+                nsamples = buffer_len - filled;
+            }
+        }
+
+        SDL_UnlockMutex(callback_queue_mutex);
+
+        // Add emulator output to buffer.
+
+        FillBuffer(buffer + filled * 2, nsamples);
+        filled += nsamples;
+
+        // Invoke callbacks for this point in time.
+
+        AdvanceTime(nsamples);
+    }
+}
+
+static void OPL_SDL_Shutdown(void)
+{
+    Mix_HookMusic(NULL, NULL);
+
+    if (sdl_was_initialized)
+    {
+        Mix_CloseAudio();
+        SDL_QuitSubSystem(SDL_INIT_AUDIO);
+        OPL_Queue_Destroy(callback_queue);
+        free(mix_buffer);
+        sdl_was_initialized = 0;
+    }
+
+    if (opl_emulator != NULL)
+    {
+        OPLDestroy(opl_emulator);
+        opl_emulator = NULL;
+    }
+
+    if (callback_mutex != NULL)
+    {
+        SDL_DestroyMutex(callback_mutex);
+        callback_mutex = NULL;
+    }
+
+    if (callback_queue_mutex != NULL)
+    {
+        SDL_DestroyMutex(callback_queue_mutex);
+        callback_queue_mutex = NULL;
+    }
+}
+
+// Callback when a timer expires.
+
+static void TimerOver(void *data)
+{
+    int channel = (int) data;
+
+    OPLTimerOver(opl_emulator, channel);
+}
+
+// Callback invoked when the emulator code wants to set a timer.
+
+static void TimerHandler(int channel, double interval_seconds)
+{
+    unsigned int interval_samples;
+
+    interval_samples = (int) (interval_seconds * mixing_freq);
+
+    SDL_LockMutex(callback_queue_mutex);
+    OPL_Queue_Push(callback_queue, TimerOver, (void *) channel,
+                   current_time - pause_offset + interval_samples);
+    SDL_UnlockMutex(callback_queue_mutex);
+}
+
+static unsigned int GetSliceSize(void)
+{
+    int limit;
+    int n;
+
+    limit = (opl_sample_rate * MAX_SOUND_SLICE_TIME) / 1000;
+
+    // Try all powers of two, not exceeding the limit.
+
+    for (n=0;; ++n)
+    {
+        // 2^n <= limit < 2^n+1 ?
+
+        if ((1 << (n + 1)) > limit)
+        {
+            return (1 << n);
+        }
+    }
+
+    // Should never happen?
+
+    return 1024;
+}
+
+static int OPL_SDL_Init(unsigned int port_base)
+{
+    // Check if SDL_mixer has been opened already
+    // If not, we must initialize it now
+
+    if (!SDLIsInitialized())
+    {
+        if (SDL_Init(SDL_INIT_AUDIO) < 0)
+        {
+            fprintf(stderr, "Unable to set up sound.\n");
+            return 0;
+        }
+
+        if (Mix_OpenAudio(opl_sample_rate, AUDIO_S16SYS, 2, GetSliceSize()) < 0)
+        {
+            fprintf(stderr, "Error initialising SDL_mixer: %s\n", Mix_GetError());
+
+            SDL_QuitSubSystem(SDL_INIT_AUDIO);
+            return 0;
+        }
+
+        SDL_PauseAudio(0);
+
+        // When this module shuts down, it has the responsibility to 
+        // shut down SDL.
+
+        sdl_was_initialized = 1;
+    }
+    else
+    {
+        sdl_was_initialized = 0;
+    }
+
+    opl_sdl_paused = 0;
+    pause_offset = 0;
+
+    // Queue structure of callbacks to invoke.
+
+    callback_queue = OPL_Queue_Create();
+    current_time = 0;
+
+    // Get the mixer frequency, format and number of channels.
+
+    Mix_QuerySpec(&mixing_freq, &mixing_format, &mixing_channels);
+
+    // Only supports AUDIO_S16SYS
+
+    if (mixing_format != AUDIO_S16SYS || mixing_channels != 2)
+    {
+        fprintf(stderr, 
+                "OPL_SDL only supports native signed 16-bit LSB, "
+                "stereo format!\n");
+
+        OPL_SDL_Shutdown();
+        return 0;
+    }
+
+    // Mix buffer:
+
+    mix_buffer = malloc(mixing_freq * 2);
+
+    // Create the emulator structure:
+
+    opl_emulator = makeAdlibOPL(mixing_freq);
+
+    if (opl_emulator == NULL)
+    {
+        fprintf(stderr, "Failed to initialize software OPL emulator!\n");
+        OPL_SDL_Shutdown();
+        return 0;
+    }
+
+    OPLSetTimerHandler(opl_emulator, TimerHandler, 0);
+
+    callback_mutex = SDL_CreateMutex();
+    callback_queue_mutex = SDL_CreateMutex();
+
+    // TODO: This should be music callback? or-?
+    Mix_HookMusic(OPL_Mix_Callback, NULL);
+
+    return 1;
+}
+
+static unsigned int OPL_SDL_PortRead(opl_port_t port)
+{
+    if (opl_emulator != NULL)
+    {
+        return OPLRead(opl_emulator, port);
+    }
+    else
+    {
+        return 0;
+    }
+}
+
+static void OPL_SDL_PortWrite(opl_port_t port, unsigned int value)
+{
+    if (opl_emulator != NULL)
+    {
+        OPLWrite(opl_emulator, port, value);
+    }
+}
+
+static void OPL_SDL_SetCallback(unsigned int ms,
+                                opl_callback_t callback,
+                                void *data)
+{
+    SDL_LockMutex(callback_queue_mutex);
+    OPL_Queue_Push(callback_queue, callback, data,
+                   current_time - pause_offset + (ms * mixing_freq) / 1000);
+    SDL_UnlockMutex(callback_queue_mutex);
+}
+
+static void OPL_SDL_ClearCallbacks(void)
+{
+    SDL_LockMutex(callback_queue_mutex);
+    OPL_Queue_Clear(callback_queue);
+    SDL_UnlockMutex(callback_queue_mutex);
+}
+
+static void OPL_SDL_Lock(void)
+{
+    SDL_LockMutex(callback_mutex);
+}
+
+static void OPL_SDL_Unlock(void)
+{
+    SDL_UnlockMutex(callback_mutex);
+}
+
+static void OPL_SDL_SetPaused(int paused)
+{
+    opl_sdl_paused = paused;
+}
+
+opl_driver_t opl_sdl_driver =
+{
+    "SDL",
+    OPL_SDL_Init,
+    OPL_SDL_Shutdown,
+    OPL_SDL_PortRead,
+    OPL_SDL_PortWrite,
+    OPL_SDL_SetCallback,
+    OPL_SDL_ClearCallbacks,
+    OPL_SDL_Lock,
+    OPL_SDL_Unlock,
+    OPL_SDL_SetPaused
+};
+
diff --git a/opl/opl_timer.c b/opl/opl_timer.c
new file mode 100644
index 00000000..35b2092f
--- /dev/null
+++ b/opl/opl_timer.c
@@ -0,0 +1,251 @@
+// Emacs style mode select   -*- C++ -*- 
+//-----------------------------------------------------------------------------
+//
+// Copyright(C) 2009 Simon Howard
+//
+// This program is free software; you can redistribute it and/or
+// modify it under the terms of the GNU General Public License
+// as published by the Free Software Foundation; either version 2
+// of the License, or (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with this program; if not, write to the Free Software
+// Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
+// 02111-1307, USA.
+//
+// DESCRIPTION:
+//     OPL timer thread.
+//     Once started using OPL_Timer_StartThread, the thread sleeps,
+//     waking up to invoke callbacks set using OPL_Timer_SetCallback.
+//
+//-----------------------------------------------------------------------------
+
+#include "SDL.h"
+
+#include "opl_timer.h"
+#include "opl_queue.h"
+
+typedef enum
+{
+    THREAD_STATE_STOPPED,
+    THREAD_STATE_RUNNING,
+    THREAD_STATE_STOPPING,
+} thread_state_t;
+
+static SDL_Thread *timer_thread = NULL;
+static thread_state_t timer_thread_state;
+static int current_time;
+
+// If non-zero, callbacks are currently paused.
+
+static int opl_timer_paused;
+
+// Offset in milliseconds to adjust time due to the fact that playback
+// was paused.
+
+static unsigned int pause_offset = 0;
+
+// Queue of callbacks waiting to be invoked.
+// The callback queue mutex is held while the callback queue structure
+// or current_time is being accessed.
+
+static opl_callback_queue_t *callback_queue;
+static SDL_mutex *callback_queue_mutex;
+
+// The timer mutex is held while timer callback functions are being
+// invoked, so that the calling code can prevent clashes.
+
+static SDL_mutex *timer_mutex;
+
+// Returns true if there is a callback at the head of the queue ready
+// to be invoked.  Otherwise, next_time is set to the time when the
+// timer thread must wake up again to check.
+
+static int CallbackWaiting(unsigned int *next_time)
+{
+    // If paused, just wait in 50ms increments until unpaused.
+    // Update pause_offset so after we unpause, the callback 
+    // times will be right.
+
+    if (opl_timer_paused)
+    {
+        *next_time = current_time + 50;
+        pause_offset += 50;
+        return 0;
+    }
+
+    // If there are no queued callbacks, sleep for 50ms at a time
+    // until a callback is added.
+
+    if (OPL_Queue_IsEmpty(callback_queue))
+    {
+        *next_time = current_time + 50;
+        return 0;
+    }
+
+    // Read the time of the first callback in the queue.
+    // If the time for the callback has not yet arrived,
+    // we must sleep until the callback time.
+
+    *next_time = OPL_Queue_Peek(callback_queue) + pause_offset;
+
+    return *next_time <= current_time;
+}
+
+static unsigned int GetNextTime(void)
+{
+    opl_callback_t callback;
+    void *callback_data;
+    unsigned int next_time;
+    int have_callback;
+
+    // Keep running through callbacks until there are none ready to
+    // run. When we run out of callbacks, next_time will be set.
+
+    do
+    {
+        SDL_LockMutex(callback_queue_mutex);
+
+        // Check if the callback at the head of the list is ready to
+        // be invoked.  If so, pop from the head of the queue.
+
+        have_callback = CallbackWaiting(&next_time);
+
+        if (have_callback)
+        {
+            OPL_Queue_Pop(callback_queue, &callback, &callback_data);
+        }
+
+        SDL_UnlockMutex(callback_queue_mutex);
+
+        // Now invoke the callback, if we have one.
+        // The timer mutex is held while the callback is invoked.
+
+        if (have_callback)
+        {
+            SDL_LockMutex(timer_mutex);
+            callback(callback_data);
+            SDL_UnlockMutex(timer_mutex);
+        }
+    } while (have_callback);
+
+    return next_time;
+}
+
+static int ThreadFunction(void *unused)
+{
+    unsigned int next_time;
+    unsigned int now;
+
+    // Keep running until OPL_Timer_StopThread is called.
+
+    while (timer_thread_state == THREAD_STATE_RUNNING)
+    {
+        // Get the next time that we must sleep until, and
+        // wait until that time.
+
+        next_time = GetNextTime();
+        now = SDL_GetTicks();
+
+        if (next_time > now)
+        {
+            SDL_Delay(next_time - now);
+        }
+
+        // Update the current time.
+
+        SDL_LockMutex(callback_queue_mutex);
+        current_time = next_time;
+        SDL_UnlockMutex(callback_queue_mutex);
+    }
+
+    timer_thread_state = THREAD_STATE_STOPPED;
+
+    return 0;
+}
+
+static void InitResources(void)
+{
+    callback_queue = OPL_Queue_Create();
+    timer_mutex = SDL_CreateMutex();
+    callback_queue_mutex = SDL_CreateMutex();
+}
+
+static void FreeResources(void)
+{
+    OPL_Queue_Destroy(callback_queue);
+    SDL_DestroyMutex(callback_queue_mutex);
+    SDL_DestroyMutex(timer_mutex);
+}
+
+int OPL_Timer_StartThread(void)
+{
+    InitResources();
+
+    timer_thread_state = THREAD_STATE_RUNNING;
+    current_time = SDL_GetTicks();
+    opl_timer_paused = 0;
+    pause_offset = 0;
+
+    timer_thread = SDL_CreateThread(ThreadFunction, NULL);
+
+    if (timer_thread == NULL)
+    {
+        timer_thread_state = THREAD_STATE_STOPPED;
+        FreeResources();
+
+        return 0;
+    }
+
+    return 1;
+}
+
+void OPL_Timer_StopThread(void)
+{
+    timer_thread_state = THREAD_STATE_STOPPING;
+
+    while (timer_thread_state != THREAD_STATE_STOPPED)
+    {
+        SDL_Delay(1);
+    }
+
+    FreeResources();
+}
+
+void OPL_Timer_SetCallback(unsigned int ms, opl_callback_t callback, void *data)
+{
+    SDL_LockMutex(callback_queue_mutex);
+    OPL_Queue_Push(callback_queue, callback, data,
+                   current_time + ms - pause_offset);
+    SDL_UnlockMutex(callback_queue_mutex);
+}
+
+void OPL_Timer_ClearCallbacks(void)
+{
+    SDL_LockMutex(callback_queue_mutex);
+    OPL_Queue_Clear(callback_queue);
+    SDL_UnlockMutex(callback_queue_mutex);
+}
+
+void OPL_Timer_Lock(void)
+{
+    SDL_LockMutex(timer_mutex);
+}
+
+void OPL_Timer_Unlock(void)
+{
+    SDL_UnlockMutex(timer_mutex);
+}
+
+void OPL_Timer_SetPaused(int paused)
+{
+    SDL_LockMutex(callback_queue_mutex);
+    opl_timer_paused = paused;
+    SDL_UnlockMutex(callback_queue_mutex);
+}
+
diff --git a/opl/opl_timer.h b/opl/opl_timer.h
new file mode 100644
index 00000000..f03fc499
--- /dev/null
+++ b/opl/opl_timer.h
@@ -0,0 +1,42 @@
+// Emacs style mode select   -*- C++ -*- 
+//-----------------------------------------------------------------------------
+//
+// Copyright(C) 2009 Simon Howard
+//
+// This program is free software; you can redistribute it and/or
+// modify it under the terms of the GNU General Public License
+// as published by the Free Software Foundation; either version 2
+// of the License, or (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with this program; if not, write to the Free Software
+// Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
+// 02111-1307, USA.
+//
+// DESCRIPTION:
+//     OPL timer thread.
+//
+//-----------------------------------------------------------------------------
+
+#ifndef OPL_TIMER_H
+#define OPL_TIMER_H
+
+#include "opl.h"
+
+int OPL_Timer_StartThread(void);
+void OPL_Timer_StopThread(void);
+void OPL_Timer_SetCallback(unsigned int ms,
+                           opl_callback_t callback,
+                           void *data);
+void OPL_Timer_ClearCallbacks(void);
+void OPL_Timer_Lock(void);
+void OPL_Timer_Unlock(void);
+void OPL_Timer_SetPaused(int paused);
+
+#endif /* #ifndef OPL_TIMER_H */
+
diff --git a/opl/opl_win32.c b/opl/opl_win32.c
new file mode 100644
index 00000000..29df3643
--- /dev/null
+++ b/opl/opl_win32.c
@@ -0,0 +1,172 @@
+// Emacs style mode select   -*- C++ -*- 
+//-----------------------------------------------------------------------------
+//
+// Copyright(C) 2009 Simon Howard
+//
+// This program is free software; you can redistribute it and/or
+// modify it under the terms of the GNU General Public License
+// as published by the Free Software Foundation; either version 2
+// of the License, or (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with this program; if not, write to the Free Software
+// Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
+// 02111-1307, USA.
+//
+// DESCRIPTION:
+//     OPL Win32 native interface.
+//
+//-----------------------------------------------------------------------------
+
+#include "config.h"
+
+#ifdef _WIN32
+
+#include <stdio.h>
+
+#define WIN32_LEAN_AND_MEAN
+#include <windows.h>
+
+#include "opl.h"
+#include "opl_internal.h"
+#include "opl_timer.h"
+
+#include "ioperm_sys.h"
+
+static unsigned int opl_port_base;
+
+// MingW?
+
+#if defined(__GNUC__) && defined(__i386__)
+
+static unsigned int OPL_Win32_PortRead(opl_port_t port)
+{
+    unsigned char result;
+
+    __asm__ volatile (
+       "movl %1, %%edx\n"
+       "inb  %%dx, %%al\n"
+       "movb %%al, %0"
+       :   "=m" (result)
+       :   "r" (opl_port_base + port)
+       :   "edx", "al", "memory"
+    );
+
+    return result;
+}
+
+static void OPL_Win32_PortWrite(opl_port_t port, unsigned int value)
+{
+    __asm__ volatile (
+       "movl %0, %%edx\n"
+       "movb %1, %%al\n"
+       "outb %%al, %%dx"
+       :
+       :   "r" (opl_port_base + port), "r" ((unsigned char) value)
+       :   "edx", "al"
+    );
+}
+
+// TODO: MSVC version
+// #elif defined(_MSC_VER) && defined(_M_IX6) ...
+
+#else
+
+// Not x86, or don't know how to do port R/W on this compiler.
+
+#define NO_PORT_RW
+
+static unsigned int OPL_Win32_PortRead(opl_port_t port)
+{
+    return 0;
+}
+
+static void OPL_Win32_PortWrite(opl_port_t port, unsigned int value)
+{
+}
+
+#endif
+
+static int OPL_Win32_Init(unsigned int port_base)
+{
+#ifndef NO_PORT_RW
+
+    OSVERSIONINFO version_info;
+
+    opl_port_base = port_base;
+
+    // Check the OS version.
+
+    memset(&version_info, 0, sizeof(version_info));
+    version_info.dwOSVersionInfoSize = sizeof(version_info);
+
+    GetVersionEx(&version_info);
+
+    // On NT-based systems, we must acquire I/O port permissions
+    // using the ioperm.sys driver.
+
+    if (version_info.dwPlatformId == VER_PLATFORM_WIN32_NT)
+    {
+        // Install driver.
+
+        if (!IOperm_InstallDriver())
+        {
+            return 0;
+        }
+
+        // Open port range.
+
+        if (!IOperm_EnablePortRange(opl_port_base, 2, 1))
+        {
+            IOperm_UninstallDriver();
+            return 0;
+        }
+    }
+
+    // Start callback thread
+
+    if (!OPL_Timer_StartThread())
+    {
+        IOperm_UninstallDriver();
+        return 0;
+    }
+
+    return 1;
+
+#endif
+
+    return 0;
+}
+
+static void OPL_Win32_Shutdown(void)
+{
+    // Stop callback thread
+
+    OPL_Timer_StopThread();
+
+    // Unload IOperm library.
+
+    IOperm_UninstallDriver();
+}
+
+opl_driver_t opl_win32_driver =
+{
+    "Win32",
+    OPL_Win32_Init,
+    OPL_Win32_Shutdown,
+    OPL_Win32_PortRead,
+    OPL_Win32_PortWrite,
+    OPL_Timer_SetCallback,
+    OPL_Timer_ClearCallbacks,
+    OPL_Timer_Lock,
+    OPL_Timer_Unlock,
+    OPL_Timer_SetPaused
+};
+
+#endif /* #ifdef _WIN32 */
+
diff --git a/pkg/win32/GNUmakefile b/pkg/win32/GNUmakefile
index 626f1845..31968795 100644
--- a/pkg/win32/GNUmakefile
+++ b/pkg/win32/GNUmakefile
@@ -11,6 +11,8 @@ DLL_FILES=$(TOPLEVEL)/src/SDL.dll                      \
           $(TOPLEVEL)/src/SDL_mixer.dll                \
           $(TOPLEVEL)/src/SDL_net.dll
 
+DOC_FILES += README.OPL
+
 ZIP=$(PACKAGE_TARNAME)-$(PACKAGE_VERSION)-win32.zip
 
 $(ZIP) : staging
diff --git a/rpm.spec.in b/rpm.spec.in
index 1b7e90c7..58142c1b 100644
--- a/rpm.spec.in
+++ b/rpm.spec.in
@@ -52,6 +52,7 @@ rm -rf $RPM_BUILD_ROOT
 %doc NEWS
 %doc AUTHORS
 %doc README
+%doc README.OPL
 %doc COPYING
 %doc CMDLINE
 %doc BUGS
diff --git a/setup/sound.c b/setup/sound.c
index 9e02aeec..0ca95b08 100644
--- a/setup/sound.c
+++ b/setup/sound.c
@@ -35,6 +35,14 @@ typedef enum
     NUM_SFXMODES
 } sfxmode_t;
 
+typedef enum
+{
+    MUSMODE_DISABLED,
+    MUSMODE_OPL,
+    MUSMODE_NATIVE,
+    NUM_MUSMODES
+} musmode_t;
+
 static char *sfxmode_strings[] = 
 {
     "Disabled",
@@ -42,6 +50,13 @@ static char *sfxmode_strings[] =
     "Digital",
 };
 
+static char *musmode_strings[] =
+{
+    "Disabled",
+    "OPL (Adlib/SB)",
+    "Native MIDI"
+};
+
 int snd_sfxdevice = SNDDEVICE_SB;
 int numChannels = 8;
 int sfxVolume = 15;
@@ -54,7 +69,7 @@ int snd_samplerate = 22050;
 int use_libsamplerate = 0;
 
 static int snd_sfxmode;
-static int snd_musicenabled;
+static int snd_musmode;
 
 static void UpdateSndDevices(TXT_UNCAST_ARG(widget), TXT_UNCAST_ARG(data))
 {
@@ -70,14 +85,18 @@ static void UpdateSndDevices(TXT_UNCAST_ARG(widget), TXT_UNCAST_ARG(data))
             snd_sfxdevice = SNDDEVICE_SB;
             break;
     }
-    
-    if (snd_musicenabled)
-    {
-        snd_musicdevice = SNDDEVICE_SB;
-    }
-    else
+
+    switch (snd_musmode)
     {
-        snd_musicdevice = SNDDEVICE_NONE;
+        case MUSMODE_DISABLED:
+            snd_musicdevice = SNDDEVICE_NONE;
+            break;
+        case MUSMODE_OPL:
+            snd_musicdevice = SNDDEVICE_SB;
+            break;
+        case MUSMODE_NATIVE:
+            snd_musicdevice = SNDDEVICE_GENMIDI;
+            break;
     }
 }
 
@@ -87,7 +106,7 @@ void ConfigSound(void)
     txt_table_t *sfx_table;
     txt_table_t *music_table;
     txt_dropdown_list_t *sfx_mode_control;
-    txt_checkbox_t *music_enabled_control;
+    txt_dropdown_list_t *mus_mode_control;
 
     if (snd_sfxdevice == SNDDEVICE_PCSPEAKER)
     {
@@ -101,8 +120,21 @@ void ConfigSound(void)
     {
         snd_sfxmode = SFXMODE_DISABLED;
     }
-    
-    snd_musicenabled = snd_musicdevice != SNDDEVICE_NONE;
+
+    if (snd_musicdevice == SNDDEVICE_GENMIDI)
+    {
+        snd_musmode = MUSMODE_NATIVE;
+    }
+    else if (snd_musicdevice == SNDDEVICE_SB
+          || snd_musicdevice == SNDDEVICE_ADLIB
+          || snd_musicdevice == SNDDEVICE_AWE32)
+    {
+        snd_musmode = MUSMODE_OPL;
+    }
+    else
+    {
+        snd_musmode = MUSMODE_DISABLED;
+    }
 
     window = TXT_NewWindow("Sound configuration");
 
@@ -110,12 +142,10 @@ void ConfigSound(void)
                TXT_NewSeparator("Sound effects"),
                sfx_table = TXT_NewTable(2),
                TXT_NewSeparator("Music"),
-               music_enabled_control = TXT_NewCheckBox("Music enabled", 
-                                                       &snd_musicenabled),
                music_table = TXT_NewTable(2),
                NULL);
 
-    TXT_SetColumnWidths(sfx_table, 20, 5);
+    TXT_SetColumnWidths(sfx_table, 20, 14);
 
     TXT_AddWidgets(sfx_table, 
                    TXT_NewLabel("Sound effects"),
@@ -128,17 +158,20 @@ void ConfigSound(void)
                    TXT_NewSpinControl(&sfxVolume, 0, 15),
                    NULL);
 
-    TXT_SetColumnWidths(music_table, 20, 5);
+    TXT_SetColumnWidths(music_table, 20, 14);
 
     TXT_AddWidgets(music_table,
+                   TXT_NewLabel("Music playback"),
+                   mus_mode_control = TXT_NewDropdownList(&snd_musmode,
+                                                          musmode_strings,
+                                                          NUM_MUSMODES),
                    TXT_NewLabel("Music volume"),
                    TXT_NewSpinControl(&musicVolume, 0, 15),
                    NULL);
 
-    TXT_SignalConnect(sfx_mode_control, "changed", 
+    TXT_SignalConnect(sfx_mode_control, "changed",
                       UpdateSndDevices, NULL);
-    TXT_SignalConnect(music_enabled_control, "changed", 
+    TXT_SignalConnect(mus_mode_control, "changed",
                       UpdateSndDevices, NULL);
-
 }
 
diff --git a/src/Makefile.am b/src/Makefile.am
index 378ad053..8b827131 100644
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -3,7 +3,7 @@ gamesdir = $(prefix)/games
 
 games_PROGRAMS = chocolate-doom chocolate-server
 
-AM_CFLAGS = -I../textscreen -I../pcsound @SDLMIXER_CFLAGS@ @SDLNET_CFLAGS@
+AM_CFLAGS = -I../opl -I../textscreen -I../pcsound @SDLMIXER_CFLAGS@ @SDLNET_CFLAGS@
 
 DEDSERV_FILES=\
 d_dedicated.c                              \
@@ -155,6 +155,8 @@ FEATURE_SOUND_SOURCE_FILES =               \
 i_pcsound.c                                \
 i_sdlsound.c                               \
 i_sdlmusic.c                               \
+i_oplmusic.c                               \
+midifile.c           midifile.h            \
 mus2mid.c            mus2mid.h
 
 SOURCE_FILES = $(MAIN_SOURCE_FILES)                \
@@ -173,6 +175,7 @@ chocolate_doom_LDADD =                               \
                        ../wince/libc_wince.a         \
                        ../textscreen/libtextscreen.a \
                        ../pcsound/libpcsound.a       \
+                       ../opl/libopl.a               \
                        @LDFLAGS@                     \
                        @SDLMIXER_LIBS@               \
                        @SDLNET_LIBS@
@@ -193,3 +196,6 @@ icon.c : ../data/doom8.ico
 
 endif
 
+midiread : midifile.c
+	$(CC) -DTEST $(CFLAGS) @LDFLAGS@ $^ -o $@
+
diff --git a/src/i_oplmusic.c b/src/i_oplmusic.c
new file mode 100644
index 00000000..9501d51d
--- /dev/null
+++ b/src/i_oplmusic.c
@@ -0,0 +1,1457 @@
+// Emacs style mode select   -*- C++ -*- 
+//-----------------------------------------------------------------------------
+//
+// Copyright(C) 1993-1996 Id Software, Inc.
+// Copyright(C) 2005 Simon Howard
+//
+// This program is free software; you can redistribute it and/or
+// modify it under the terms of the GNU General Public License
+// as published by the Free Software Foundation; either version 2
+// of the License, or (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with this program; if not, write to the Free Software
+// Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
+// 02111-1307, USA.
+//
+// DESCRIPTION:
+//	System interface for music.
+//
+//-----------------------------------------------------------------------------
+
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include "doomdef.h"
+#include "memio.h"
+#include "mus2mid.h"
+
+#include "deh_main.h"
+#include "i_swap.h"
+#include "m_misc.h"
+#include "s_sound.h"
+#include "w_wad.h"
+#include "z_zone.h"
+
+#include "opl.h"
+#include "midifile.h"
+
+#define MAXMIDLENGTH (96 * 1024)
+#define GENMIDI_NUM_INSTRS  128
+
+#define GENMIDI_HEADER          "#OPL_II#"
+#define GENMIDI_FLAG_FIXED      0x0001         /* fixed pitch */
+#define GENMIDI_FLAG_2VOICE     0x0004         /* double voice (OPL3) */
+
+typedef struct
+{
+    byte tremolo;
+    byte attack;
+    byte sustain;
+    byte waveform;
+    byte scale;
+    byte level;
+} PACKEDATTR genmidi_op_t;
+
+typedef struct
+{
+    genmidi_op_t modulator;
+    byte feedback;
+    genmidi_op_t carrier;
+    byte unused;
+    short base_note_offset;
+} PACKEDATTR genmidi_voice_t;
+
+typedef struct
+{
+    unsigned short flags;
+    byte fine_tuning;
+    byte fixed_note;
+
+    genmidi_voice_t voices[2];
+} PACKEDATTR genmidi_instr_t;
+
+// Data associated with a channel of a track that is currently playing.
+
+typedef struct
+{
+    // The instrument currently used for this track.
+
+    genmidi_instr_t *instrument;
+
+    // Volume level
+
+    int volume;
+
+    // Pitch bend value:
+
+    int bend;
+
+} opl_channel_data_t;
+
+// Data associated with a track that is currently playing.
+
+typedef struct
+{
+    // Data for each channel.
+
+    opl_channel_data_t channels[MIDI_CHANNELS_PER_TRACK];
+
+    // Track iterator used to read new events.
+
+    midi_track_iter_t *iter;
+
+    // Tempo control variables
+
+    unsigned int ticks_per_beat;
+    unsigned int ms_per_beat;
+} opl_track_data_t;
+
+typedef struct opl_voice_s opl_voice_t;
+
+struct opl_voice_s
+{
+    // Index of this voice:
+    int index;
+
+    // The operators used by this voice:
+    int op1, op2;
+
+    // Currently-loaded instrument data
+    genmidi_instr_t *current_instr;
+
+    // The voice number in the instrument to use.
+    // This is normally set to zero; if this is a double voice
+    // instrument, it may be one.
+    unsigned int current_instr_voice;
+
+    // The channel currently using this voice.
+    opl_channel_data_t *channel;
+
+    // The midi key that this voice is playing.
+    unsigned int key;
+
+    // The note being played.  This is normally the same as
+    // the key, but if the instrument is a fixed pitch
+    // instrument, it is different.
+    unsigned int note;
+
+    // The frequency value being used.
+    unsigned int freq;
+
+    // The volume of the note being played on this channel.
+    unsigned int note_volume;
+
+    // The current volume (register value) that has been set for this channel.
+    unsigned int reg_volume;
+
+    // Next in linked list; a voice is always either in the
+    // free list or the allocated list.
+    opl_voice_t *next;
+};
+
+// Operators used by the different voices.
+
+static const int voice_operators[2][OPL_NUM_VOICES] = {
+    { 0x00, 0x01, 0x02, 0x08, 0x09, 0x0a, 0x10, 0x11, 0x12 },
+    { 0x03, 0x04, 0x05, 0x0b, 0x0c, 0x0d, 0x13, 0x14, 0x15 }
+};
+
+// Frequency values to use for each note.
+
+static const unsigned short frequency_curve[] = {
+
+    0x133, 0x133, 0x134, 0x134, 0x135, 0x136, 0x136, 0x137,   // -1
+    0x137, 0x138, 0x138, 0x139, 0x139, 0x13a, 0x13b, 0x13b,
+    0x13c, 0x13c, 0x13d, 0x13d, 0x13e, 0x13f, 0x13f, 0x140,
+    0x140, 0x141, 0x142, 0x142, 0x143, 0x143, 0x144, 0x144,
+
+    0x145, 0x146, 0x146, 0x147, 0x147, 0x148, 0x149, 0x149,   // -2
+    0x14a, 0x14a, 0x14b, 0x14c, 0x14c, 0x14d, 0x14d, 0x14e,
+    0x14f, 0x14f, 0x150, 0x150, 0x151, 0x152, 0x152, 0x153,
+    0x153, 0x154, 0x155, 0x155, 0x156, 0x157, 0x157, 0x158,
+
+    // These are used for the first seven MIDI note values:
+
+    0x158, 0x159, 0x15a, 0x15a, 0x15b, 0x15b, 0x15c, 0x15d,   // 0
+    0x15d, 0x15e, 0x15f, 0x15f, 0x160, 0x161, 0x161, 0x162,
+    0x162, 0x163, 0x164, 0x164, 0x165, 0x166, 0x166, 0x167,
+    0x168, 0x168, 0x169, 0x16a, 0x16a, 0x16b, 0x16c, 0x16c,
+
+    0x16d, 0x16e, 0x16e, 0x16f, 0x170, 0x170, 0x171, 0x172,   // 1
+    0x172, 0x173, 0x174, 0x174, 0x175, 0x176, 0x176, 0x177,
+    0x178, 0x178, 0x179, 0x17a, 0x17a, 0x17b, 0x17c, 0x17c,
+    0x17d, 0x17e, 0x17e, 0x17f, 0x180, 0x181, 0x181, 0x182,
+
+    0x183, 0x183, 0x184, 0x185, 0x185, 0x186, 0x187, 0x188,   // 2
+    0x188, 0x189, 0x18a, 0x18a, 0x18b, 0x18c, 0x18d, 0x18d,
+    0x18e, 0x18f, 0x18f, 0x190, 0x191, 0x192, 0x192, 0x193,
+    0x194, 0x194, 0x195, 0x196, 0x197, 0x197, 0x198, 0x199,
+
+    0x19a, 0x19a, 0x19b, 0x19c, 0x19d, 0x19d, 0x19e, 0x19f,   // 3
+    0x1a0, 0x1a0, 0x1a1, 0x1a2, 0x1a3, 0x1a3, 0x1a4, 0x1a5,
+    0x1a6, 0x1a6, 0x1a7, 0x1a8, 0x1a9, 0x1a9, 0x1aa, 0x1ab,
+    0x1ac, 0x1ad, 0x1ad, 0x1ae, 0x1af, 0x1b0, 0x1b0, 0x1b1,
+
+    0x1b2, 0x1b3, 0x1b4, 0x1b4, 0x1b5, 0x1b6, 0x1b7, 0x1b8,   // 4
+    0x1b8, 0x1b9, 0x1ba, 0x1bb, 0x1bc, 0x1bc, 0x1bd, 0x1be,
+    0x1bf, 0x1c0, 0x1c0, 0x1c1, 0x1c2, 0x1c3, 0x1c4, 0x1c4,
+    0x1c5, 0x1c6, 0x1c7, 0x1c8, 0x1c9, 0x1c9, 0x1ca, 0x1cb,
+
+    0x1cc, 0x1cd, 0x1ce, 0x1ce, 0x1cf, 0x1d0, 0x1d1, 0x1d2,   // 5
+    0x1d3, 0x1d3, 0x1d4, 0x1d5, 0x1d6, 0x1d7, 0x1d8, 0x1d8,
+    0x1d9, 0x1da, 0x1db, 0x1dc, 0x1dd, 0x1de, 0x1de, 0x1df,
+    0x1e0, 0x1e1, 0x1e2, 0x1e3, 0x1e4, 0x1e5, 0x1e5, 0x1e6,
+
+    0x1e7, 0x1e8, 0x1e9, 0x1ea, 0x1eb, 0x1ec, 0x1ed, 0x1ed,   // 6
+    0x1ee, 0x1ef, 0x1f0, 0x1f1, 0x1f2, 0x1f3, 0x1f4, 0x1f5,
+    0x1f6, 0x1f6, 0x1f7, 0x1f8, 0x1f9, 0x1fa, 0x1fb, 0x1fc,
+    0x1fd, 0x1fe, 0x1ff, 0x200, 0x201, 0x201, 0x202, 0x203,
+
+    // First note of looped range used for all octaves:
+
+    0x204, 0x205, 0x206, 0x207, 0x208, 0x209, 0x20a, 0x20b,   // 7
+    0x20c, 0x20d, 0x20e, 0x20f, 0x210, 0x210, 0x211, 0x212,
+    0x213, 0x214, 0x215, 0x216, 0x217, 0x218, 0x219, 0x21a,
+    0x21b, 0x21c, 0x21d, 0x21e, 0x21f, 0x220, 0x221, 0x222,
+
+    0x223, 0x224, 0x225, 0x226, 0x227, 0x228, 0x229, 0x22a,   // 8
+    0x22b, 0x22c, 0x22d, 0x22e, 0x22f, 0x230, 0x231, 0x232,
+    0x233, 0x234, 0x235, 0x236, 0x237, 0x238, 0x239, 0x23a,
+    0x23b, 0x23c, 0x23d, 0x23e, 0x23f, 0x240, 0x241, 0x242,
+
+    0x244, 0x245, 0x246, 0x247, 0x248, 0x249, 0x24a, 0x24b,   // 9
+    0x24c, 0x24d, 0x24e, 0x24f, 0x250, 0x251, 0x252, 0x253,
+    0x254, 0x256, 0x257, 0x258, 0x259, 0x25a, 0x25b, 0x25c,
+    0x25d, 0x25e, 0x25f, 0x260, 0x262, 0x263, 0x264, 0x265,
+
+    0x266, 0x267, 0x268, 0x269, 0x26a, 0x26c, 0x26d, 0x26e,   // 10
+    0x26f, 0x270, 0x271, 0x272, 0x273, 0x275, 0x276, 0x277,
+    0x278, 0x279, 0x27a, 0x27b, 0x27d, 0x27e, 0x27f, 0x280,
+    0x281, 0x282, 0x284, 0x285, 0x286, 0x287, 0x288, 0x289,
+
+    0x28b, 0x28c, 0x28d, 0x28e, 0x28f, 0x290, 0x292, 0x293,   // 11
+    0x294, 0x295, 0x296, 0x298, 0x299, 0x29a, 0x29b, 0x29c,
+    0x29e, 0x29f, 0x2a0, 0x2a1, 0x2a2, 0x2a4, 0x2a5, 0x2a6,
+    0x2a7, 0x2a9, 0x2aa, 0x2ab, 0x2ac, 0x2ae, 0x2af, 0x2b0,
+
+    0x2b1, 0x2b2, 0x2b4, 0x2b5, 0x2b6, 0x2b7, 0x2b9, 0x2ba,   // 12
+    0x2bb, 0x2bd, 0x2be, 0x2bf, 0x2c0, 0x2c2, 0x2c3, 0x2c4,
+    0x2c5, 0x2c7, 0x2c8, 0x2c9, 0x2cb, 0x2cc, 0x2cd, 0x2ce,
+    0x2d0, 0x2d1, 0x2d2, 0x2d4, 0x2d5, 0x2d6, 0x2d8, 0x2d9,
+
+    0x2da, 0x2dc, 0x2dd, 0x2de, 0x2e0, 0x2e1, 0x2e2, 0x2e4,   // 13
+    0x2e5, 0x2e6, 0x2e8, 0x2e9, 0x2ea, 0x2ec, 0x2ed, 0x2ee,
+    0x2f0, 0x2f1, 0x2f2, 0x2f4, 0x2f5, 0x2f6, 0x2f8, 0x2f9,
+    0x2fb, 0x2fc, 0x2fd, 0x2ff, 0x300, 0x302, 0x303, 0x304,
+
+    0x306, 0x307, 0x309, 0x30a, 0x30b, 0x30d, 0x30e, 0x310,   // 14
+    0x311, 0x312, 0x314, 0x315, 0x317, 0x318, 0x31a, 0x31b,
+    0x31c, 0x31e, 0x31f, 0x321, 0x322, 0x324, 0x325, 0x327,
+    0x328, 0x329, 0x32b, 0x32c, 0x32e, 0x32f, 0x331, 0x332,
+
+    0x334, 0x335, 0x337, 0x338, 0x33a, 0x33b, 0x33d, 0x33e,   // 15
+    0x340, 0x341, 0x343, 0x344, 0x346, 0x347, 0x349, 0x34a,
+    0x34c, 0x34d, 0x34f, 0x350, 0x352, 0x353, 0x355, 0x357,
+    0x358, 0x35a, 0x35b, 0x35d, 0x35e, 0x360, 0x361, 0x363,
+
+    0x365, 0x366, 0x368, 0x369, 0x36b, 0x36c, 0x36e, 0x370,   // 16
+    0x371, 0x373, 0x374, 0x376, 0x378, 0x379, 0x37b, 0x37c,
+    0x37e, 0x380, 0x381, 0x383, 0x384, 0x386, 0x388, 0x389,
+    0x38b, 0x38d, 0x38e, 0x390, 0x392, 0x393, 0x395, 0x397,
+
+    0x398, 0x39a, 0x39c, 0x39d, 0x39f, 0x3a1, 0x3a2, 0x3a4,   // 17
+    0x3a6, 0x3a7, 0x3a9, 0x3ab, 0x3ac, 0x3ae, 0x3b0, 0x3b1,
+    0x3b3, 0x3b5, 0x3b7, 0x3b8, 0x3ba, 0x3bc, 0x3bd, 0x3bf,
+    0x3c1, 0x3c3, 0x3c4, 0x3c6, 0x3c8, 0x3ca, 0x3cb, 0x3cd,
+
+    // The last note has an incomplete range, and loops round back to
+    // the start.  Note that the last value is actually a buffer overrun
+    // and does not fit with the other values.
+
+    0x3cf, 0x3d1, 0x3d2, 0x3d4, 0x3d6, 0x3d8, 0x3da, 0x3db,   // 18
+    0x3dd, 0x3df, 0x3e1, 0x3e3, 0x3e4, 0x3e6, 0x3e8, 0x3ea,
+    0x3ec, 0x3ed, 0x3ef, 0x3f1, 0x3f3, 0x3f5, 0x3f6, 0x3f8,
+    0x3fa, 0x3fc, 0x3fe, 0x36c,
+};
+
+// Mapping from MIDI volume level to OPL level value.
+
+static const unsigned int volume_mapping_table[] = {
+    0, 1, 3, 5, 6, 8, 10, 11,
+    13, 14, 16, 17, 19, 20, 22, 23,
+    25, 26, 27, 29, 30, 32, 33, 34,
+    36, 37, 39, 41, 43, 45, 47, 49,
+    50, 52, 54, 55, 57, 59, 60, 61,
+    63, 64, 66, 67, 68, 69, 71, 72,
+    73, 74, 75, 76, 77, 79, 80, 81,
+    82, 83, 84, 84, 85, 86, 87, 88,
+    89, 90, 91, 92, 92, 93, 94, 95,
+    96, 96, 97, 98, 99, 99, 100, 101,
+    101, 102, 103, 103, 104, 105, 105, 106,
+    107, 107, 108, 109, 109, 110, 110, 111,
+    112, 112, 113, 113, 114, 114, 115, 115,
+    116, 117, 117, 118, 118, 119, 119, 120,
+    120, 121, 121, 122, 122, 123, 123, 123,
+    124, 124, 125, 125, 126, 126, 127, 127
+};
+
+static boolean music_initialized = false;
+
+//static boolean musicpaused = false;
+static int current_music_volume;
+
+// GENMIDI lump instrument data:
+
+static genmidi_instr_t *main_instrs;
+static genmidi_instr_t *percussion_instrs;
+
+// Voices:
+
+static opl_voice_t voices[OPL_NUM_VOICES];
+static opl_voice_t *voice_free_list;
+static opl_voice_t *voice_alloced_list;
+
+// Track data for playing tracks:
+
+static opl_track_data_t *tracks;
+static unsigned int num_tracks = 0;
+static unsigned int running_tracks = 0;
+static boolean song_looping;
+
+// Configuration file variable, containing the port number for the
+// adlib chip.
+
+int opl_io_port = 0x388;
+
+// Load instrument table from GENMIDI lump:
+
+static boolean LoadInstrumentTable(void)
+{
+    byte *lump;
+
+    lump = W_CacheLumpName("GENMIDI", PU_STATIC);
+
+    // Check header
+
+    if (strncmp((char *) lump, GENMIDI_HEADER, strlen(GENMIDI_HEADER)) != 0)
+    {
+        W_ReleaseLumpName("GENMIDI");
+
+        return false;
+    }
+
+    main_instrs = (genmidi_instr_t *) (lump + strlen(GENMIDI_HEADER));
+    percussion_instrs = main_instrs + GENMIDI_NUM_INSTRS;
+
+    return true;
+}
+
+// Get the next available voice from the freelist.
+
+static opl_voice_t *GetFreeVoice(void)
+{
+    opl_voice_t *result;
+
+    // None available?
+
+    if (voice_free_list == NULL)
+    {
+        return NULL;
+    }
+
+    // Remove from free list
+
+    result = voice_free_list;
+    voice_free_list = voice_free_list->next;
+
+    // Add to allocated list
+
+    result->next = voice_alloced_list;
+    voice_alloced_list = result;
+
+    return result;
+}
+
+// Remove a voice from the allocated voices list.
+
+static void RemoveVoiceFromAllocedList(opl_voice_t *voice)
+{
+    opl_voice_t **rover;
+
+    rover = &voice_alloced_list;
+
+    // Search the list until we find the voice, then remove it.
+
+    while (*rover != NULL)
+    {
+        if (*rover == voice)
+        {
+            *rover = voice->next;
+            voice->next = NULL;
+            break;
+        }
+
+        rover = &(*rover)->next;
+    }
+}
+
+// Release a voice back to the freelist.
+
+static void ReleaseVoice(opl_voice_t *voice)
+{
+    opl_voice_t **rover;
+
+    voice->channel = NULL;
+    voice->note = 0;
+
+    // Remove from alloced list.
+
+    RemoveVoiceFromAllocedList(voice);
+
+    // Search to the end of the freelist (This is how Doom behaves!)
+
+    rover = &voice_free_list;
+
+    while (*rover != NULL)
+    {
+        rover = &(*rover)->next;
+    }
+
+    *rover = voice;
+    voice->next = NULL;
+}
+
+// Load data to the specified operator
+
+static void LoadOperatorData(int operator, genmidi_op_t *data,
+                             boolean max_level)
+{
+    int level;
+
+    // The scale and level fields must be combined for the level register.
+    // For the carrier wave we always set the maximum level.
+
+    level = (data->scale & 0xc0) | (data->level & 0x3f);
+
+    if (max_level)
+    {
+        level |= 0x3f;
+    }
+
+    OPL_WriteRegister(OPL_REGS_LEVEL + operator, level);
+    OPL_WriteRegister(OPL_REGS_TREMOLO + operator, data->tremolo);
+    OPL_WriteRegister(OPL_REGS_ATTACK + operator, data->attack);
+    OPL_WriteRegister(OPL_REGS_SUSTAIN + operator, data->sustain);
+    OPL_WriteRegister(OPL_REGS_WAVEFORM + operator, data->waveform);
+}
+
+// Set the instrument for a particular voice.
+
+static void SetVoiceInstrument(opl_voice_t *voice,
+                               genmidi_instr_t *instr,
+                               unsigned int instr_voice)
+{
+    genmidi_voice_t *data;
+    unsigned int modulating;
+
+    // Instrument already set for this channel?
+
+    if (voice->current_instr == instr
+     && voice->current_instr_voice == instr_voice)
+    {
+        return;
+    }
+
+    voice->current_instr = instr;
+    voice->current_instr_voice = instr_voice;
+
+    data = &instr->voices[instr_voice];
+
+    // Are we usind modulated feedback mode?
+
+    modulating = (data->feedback & 0x01) == 0;
+
+    // Doom loads the second operator first, then the first.
+    // The carrier is set to minimum volume until the voice volume
+    // is set in SetVoiceVolume (below).  If we are not using
+    // modulating mode, we must set both to minimum volume.
+
+    LoadOperatorData(voice->op2, &data->carrier, true);
+    LoadOperatorData(voice->op1, &data->modulator, !modulating);
+
+    // Set feedback register that control the connection between the
+    // two operators.  Turn on bits in the upper nybble; I think this
+    // is for OPL3, where it turns on channel A/B.
+
+    OPL_WriteRegister(OPL_REGS_FEEDBACK + voice->index,
+                      data->feedback | 0x30);
+
+    // Hack to force a volume update.
+
+    voice->reg_volume = 999;
+}
+
+static void SetVoiceVolume(opl_voice_t *voice, unsigned int volume)
+{
+    genmidi_voice_t *opl_voice;
+    unsigned int full_volume;
+    unsigned int op_volume;
+    unsigned int reg_volume;
+
+    voice->note_volume = volume;
+
+    opl_voice = &voice->current_instr->voices[voice->current_instr_voice];
+
+    // Multiply note volume and channel volume to get the actual volume.
+
+    full_volume = (volume_mapping_table[voice->note_volume]
+                   * volume_mapping_table[voice->channel->volume]
+                   * volume_mapping_table[current_music_volume]) / (127 * 127);
+
+    // The volume of each instrument can be controlled via GENMIDI:
+
+    op_volume = 0x3f - opl_voice->carrier.level;
+
+    // The volume value to use in the register:
+
+    reg_volume = (op_volume * full_volume) / 128;
+    reg_volume = (0x3f - reg_volume) | opl_voice->carrier.scale;
+
+    // Update the volume register(s) if necessary.
+
+    if (reg_volume != voice->reg_volume)
+    {
+        voice->reg_volume = reg_volume;
+
+        OPL_WriteRegister(OPL_REGS_LEVEL + voice->op2, reg_volume);
+
+        // If we are using non-modulated feedback mode, we must set the
+        // volume for both voices.
+        // Note that the same register volume value is written for
+        // both voices, always calculated from the carrier's level
+        // value.
+
+        if ((opl_voice->feedback & 0x01) != 0)
+        {
+            OPL_WriteRegister(OPL_REGS_LEVEL + voice->op1, reg_volume);
+        }
+    }
+}
+
+// Initialize the voice table and freelist
+
+static void InitVoices(void)
+{
+    int i;
+
+    // Start with an empty free list.
+
+    voice_free_list = NULL;
+
+    // Initialize each voice.
+
+    for (i=0; i<OPL_NUM_VOICES; ++i)
+    {
+        voices[i].index = i;
+        voices[i].op1 = voice_operators[0][i];
+        voices[i].op2 = voice_operators[1][i];
+        voices[i].current_instr = NULL;
+
+        // Add this voice to the freelist.
+
+        ReleaseVoice(&voices[i]);
+    }
+}
+
+// Set music volume (0 - 127)
+
+static void I_OPL_SetMusicVolume(int volume)
+{
+    unsigned int i;
+
+    // Internal state variable.
+
+    current_music_volume = volume;
+
+    // Update the volume of all voices.
+
+    for (i=0; i<OPL_NUM_VOICES; ++i)
+    {
+        if (voices[i].channel != NULL)
+        {
+            SetVoiceVolume(&voices[i], voices[i].note_volume);
+        }
+    }
+}
+
+static void VoiceKeyOff(opl_voice_t *voice)
+{
+    OPL_WriteRegister(OPL_REGS_FREQ_2 + voice->index, voice->freq >> 8);
+}
+
+// Get the frequency that we should be using for a voice.
+
+static void KeyOffEvent(opl_track_data_t *track, midi_event_t *event)
+{
+    opl_channel_data_t *channel;
+    unsigned int key;
+    unsigned int i;
+
+/*
+    printf("note off: channel %i, %i, %i\n",
+           event->data.channel.channel,
+           event->data.channel.param1,
+           event->data.channel.param2);
+*/
+
+    channel = &track->channels[event->data.channel.channel];
+    key = event->data.channel.param1;
+
+    // Turn off voices being used to play this key.
+    // If it is a double voice instrument there will be two.
+
+    for (i=0; i<OPL_NUM_VOICES; ++i)
+    {
+        if (voices[i].channel == channel && voices[i].key == key)
+        {
+            VoiceKeyOff(&voices[i]);
+
+            // Finished with this voice now.
+
+            ReleaseVoice(&voices[i]);
+        }
+    }
+}
+
+// Compare the priorities of channels, returning either -1, 0 or 1.
+
+static int CompareChannelPriorities(opl_channel_data_t *chan1,
+                                    opl_channel_data_t *chan2)
+{
+    // TODO ...
+
+    return 1;
+}
+
+// When all voices are in use, we must discard an existing voice to
+// play a new note.  Find and free an existing voice.  The channel
+// passed to the function is the channel for the new note to be
+// played.
+
+static opl_voice_t *ReplaceExistingVoice(opl_channel_data_t *channel)
+{
+    opl_voice_t *rover;
+    opl_voice_t *result;
+
+    // Check the allocated voices, if we find an instrument that is
+    // of a lower priority to the new instrument, discard it.
+    // If a voice is being used to play the second voice of an instrument,
+    // use that, as second voices are non-essential.
+    // Lower numbered MIDI channels implicitly have a higher priority
+    // than higher-numbered channels, eg. MIDI channel 1 is never
+    // discarded for MIDI channel 2.
+
+    result = NULL;
+
+    for (rover = voice_alloced_list; rover != NULL; rover = rover->next)
+    {
+        if (rover->current_instr_voice != 0
+         || (rover->channel > channel
+             && CompareChannelPriorities(channel, rover->channel) > 0))
+        {
+            result = rover;
+            break;
+        }
+    }
+
+    // If we didn't find a voice, find an existing voice being used to
+    // play a note on the same channel, and use that.
+
+    if (result == NULL)
+    {
+        for (rover = voice_alloced_list; rover != NULL; rover = rover->next)
+        {
+            if (rover->channel == channel)
+            {
+                result = rover;
+                break;
+            }
+        }
+    }
+
+    // Still nothing found?  Give up and just use the first voice in
+    // the list.
+
+    if (result == NULL)
+    {
+        result = voice_alloced_list;
+    }
+
+    // Stop playing this voice playing and release it back to the free
+    // list.
+
+    VoiceKeyOff(result);
+    ReleaseVoice(result);
+
+    // Re-allocate the voice again and return it.
+
+    return GetFreeVoice();
+}
+
+
+static unsigned int FrequencyForVoice(opl_voice_t *voice)
+{
+    genmidi_voice_t *gm_voice;
+    unsigned int freq_index;
+    unsigned int octave;
+    unsigned int sub_index;
+    unsigned int note;
+
+    note = voice->note;
+
+    // Apply note offset.
+    // Don't apply offset if the instrument is a fixed note instrument.
+
+    gm_voice = &voice->current_instr->voices[voice->current_instr_voice];
+
+    if ((voice->current_instr->flags & GENMIDI_FLAG_FIXED) == 0)
+    {
+        note += (signed short) SHORT(gm_voice->base_note_offset);
+    }
+
+    // Avoid possible overflow due to base note offset:
+
+    if (note > 0x7f)
+    {
+        note = voice->note;
+    }
+
+    freq_index = 64 + 32 * note + voice->channel->bend;
+
+    // If this is the second voice of a double voice instrument, the
+    // frequency index can be adjusted by the fine tuning field.
+
+    if (voice->current_instr_voice != 0)
+    {
+        freq_index += (voice->current_instr->fine_tuning / 2) - 64;
+    }
+
+    // The first 7 notes use the start of the table, while
+    // consecutive notes loop around the latter part.
+
+    if (freq_index < 284)
+    {
+        return frequency_curve[freq_index];
+    }
+
+    sub_index = (freq_index - 284) % (12 * 32);
+    octave = (freq_index - 284) / (12 * 32);
+
+    // Once the seventh octave is reached, things break down.
+    // We can only go up to octave 7 as a maximum anyway (the OPL
+    // register only has three bits for octave number), but for the
+    // notes in octave 7, the first five bits have octave=7, the
+    // following notes have octave=6.  This 7/6 pattern repeats in
+    // following octaves (which are technically impossible to
+    // represent anyway).
+
+    if (octave >= 7)
+    {
+        if (sub_index < 5)
+        {
+            octave = 7;
+        }
+        else
+        {
+            octave = 6;
+        }
+    }
+
+    // Calculate the resulting register value to use for the frequency.
+
+    return frequency_curve[sub_index + 284] | (octave << 10);
+}
+
+// Update the frequency that a voice is programmed to use.
+
+static void UpdateVoiceFrequency(opl_voice_t *voice)
+{
+    unsigned int freq;
+
+    // Calculate the frequency to use for this voice and update it
+    // if neccessary.
+
+    freq = FrequencyForVoice(voice);
+
+    if (voice->freq != freq)
+    {
+        OPL_WriteRegister(OPL_REGS_FREQ_1 + voice->index, freq & 0xff);
+        OPL_WriteRegister(OPL_REGS_FREQ_2 + voice->index, (freq >> 8) | 0x20);
+
+        voice->freq = freq;
+    }
+}
+
+// Program a single voice for an instrument.  For a double voice 
+// instrument (GENMIDI_FLAG_2VOICE), this is called twice for each
+// key on event.
+
+static void VoiceKeyOn(opl_channel_data_t *channel,
+                       genmidi_instr_t *instrument,
+                       unsigned int instrument_voice,
+                       unsigned int key,
+                       unsigned int volume)
+{
+    opl_voice_t *voice;
+
+    // Find a voice to use for this new note.
+
+    voice = GetFreeVoice();
+
+    // If there are no more voices left, we must decide what to do.
+    // If this is the first voice of the instrument, free an existing
+    // voice and use that.  Otherwise, if this is the second voice,
+    // it isn't as important; just discard it.
+
+    if (voice == NULL)
+    {
+        if (instrument_voice == 0)
+        {
+            voice = ReplaceExistingVoice(channel);
+        }
+        else
+        {
+            return;
+        }
+    }
+
+    voice->channel = channel;
+    voice->key = key;
+
+    // Work out the note to use.  This is normally the same as
+    // the key, unless it is a fixed pitch instrument.
+
+    if ((instrument->flags & GENMIDI_FLAG_FIXED) != 0)
+    {
+        voice->note = instrument->fixed_note;
+    }
+    else
+    {
+        voice->note = key;
+    }
+
+    // Program the voice with the instrument data:
+
+    SetVoiceInstrument(voice, instrument, instrument_voice);
+
+    // Set the volume level.
+
+    SetVoiceVolume(voice, volume);
+
+    // Write the frequency value to turn the note on.
+
+    voice->freq = 0;
+    UpdateVoiceFrequency(voice);
+}
+
+static void KeyOnEvent(opl_track_data_t *track, midi_event_t *event)
+{
+    genmidi_instr_t *instrument;
+    opl_channel_data_t *channel;
+    unsigned int key;
+    unsigned int volume;
+
+/*
+    printf("note on: channel %i, %i, %i\n",
+           event->data.channel.channel,
+           event->data.channel.param1,
+           event->data.channel.param2);
+*/
+
+    // The channel.
+
+    channel = &track->channels[event->data.channel.channel];
+    key = event->data.channel.param1;
+    volume = event->data.channel.param2;
+
+    // Percussion channel (10) is treated differently.
+
+    if (event->data.channel.channel == 9)
+    {
+        if (key < 35 || key > 81)
+        {
+            return;
+        }
+
+        instrument = &percussion_instrs[key - 35];
+    }
+    else
+    {
+        instrument = channel->instrument;
+    }
+
+    // Find and program a voice for this instrument.  If this
+    // is a double voice instrument, we must do this twice.
+
+    VoiceKeyOn(channel, instrument, 0, key, volume);
+
+    if ((instrument->flags & GENMIDI_FLAG_2VOICE) != 0)
+    {
+        VoiceKeyOn(channel, instrument, 1, key, volume);
+    }
+}
+
+static void ProgramChangeEvent(opl_track_data_t *track, midi_event_t *event)
+{
+    int channel;
+    int instrument;
+
+    // Set the instrument used on this channel.
+
+    channel = event->data.channel.channel;
+    instrument = event->data.channel.param1;
+    track->channels[channel].instrument = &main_instrs[instrument];
+
+    // TODO: Look through existing voices that are turned on on this
+    // channel, and change the instrument.
+}
+
+static void SetChannelVolume(opl_channel_data_t *channel, unsigned int volume)
+{
+    unsigned int i;
+
+    channel->volume = volume;
+
+    // Update all voices that this channel is using.
+
+    for (i=0; i<OPL_NUM_VOICES; ++i)
+    {
+        if (voices[i].channel == channel)
+        {
+            SetVoiceVolume(&voices[i], voices[i].note_volume);
+        }
+    }
+}
+
+static void ControllerEvent(opl_track_data_t *track, midi_event_t *event)
+{
+    unsigned int controller;
+    unsigned int param;
+    opl_channel_data_t *channel;
+
+/*
+    printf("change controller: channel %i, %i, %i\n",
+           event->data.channel.channel,
+           event->data.channel.param1,
+           event->data.channel.param2);
+*/
+
+    channel = &track->channels[event->data.channel.channel];
+    controller = event->data.channel.param1;
+    param = event->data.channel.param2;
+
+    switch (controller)
+    {
+        case MIDI_CONTROLLER_MAIN_VOLUME:
+            SetChannelVolume(channel, param);
+            break;
+
+        default:
+            fprintf(stderr, "Unknown MIDI controller type: %i\n", controller);
+            break;
+    }
+}
+
+// Process a pitch bend event.
+
+static void PitchBendEvent(opl_track_data_t *track, midi_event_t *event)
+{
+    opl_channel_data_t *channel;
+    unsigned int i;
+
+    // Update the channel bend value.  Only the MSB of the pitch bend
+    // value is considered: this is what Doom does.
+
+    channel = &track->channels[event->data.channel.channel];
+    channel->bend = event->data.channel.param2 - 64;
+
+    // Update all voices for this channel.
+
+    for (i=0; i<OPL_NUM_VOICES; ++i)
+    {
+        if (voices[i].channel == channel)
+        {
+            UpdateVoiceFrequency(&voices[i]);
+        }
+    }
+}
+
+// Process a meta event.
+
+static void MetaEvent(opl_track_data_t *track, midi_event_t *event)
+{
+    switch (event->data.meta.type)
+    {
+        // Things we can just ignore.
+
+        case MIDI_META_SEQUENCE_NUMBER:
+        case MIDI_META_TEXT:
+        case MIDI_META_COPYRIGHT:
+        case MIDI_META_TRACK_NAME:
+        case MIDI_META_INSTR_NAME:
+        case MIDI_META_LYRICS:
+        case MIDI_META_MARKER:
+        case MIDI_META_CUE_POINT:
+        case MIDI_META_SEQUENCER_SPECIFIC:
+            break;
+
+        // End of track - actually handled when we run out of events
+        // in the track, see below.
+
+        case MIDI_META_END_OF_TRACK:
+            break;
+
+        default:
+            fprintf(stderr, "Unknown MIDI meta event type: %i\n",
+                            event->data.meta.type);
+            break;
+    }
+}
+
+// Process a MIDI event from a track.
+
+static void ProcessEvent(opl_track_data_t *track, midi_event_t *event)
+{
+    switch (event->event_type)
+    {
+        case MIDI_EVENT_NOTE_OFF:
+            KeyOffEvent(track, event);
+            break;
+
+        case MIDI_EVENT_NOTE_ON:
+            KeyOnEvent(track, event);
+            break;
+
+        case MIDI_EVENT_CONTROLLER:
+            ControllerEvent(track, event);
+            break;
+
+        case MIDI_EVENT_PROGRAM_CHANGE:
+            ProgramChangeEvent(track, event);
+            break;
+
+        case MIDI_EVENT_PITCH_BEND:
+            PitchBendEvent(track, event);
+            break;
+
+        case MIDI_EVENT_META:
+            MetaEvent(track, event);
+            break;
+
+        // SysEx events can be ignored.
+
+        case MIDI_EVENT_SYSEX:
+        case MIDI_EVENT_SYSEX_SPLIT:
+            break;
+
+        default:
+            fprintf(stderr, "Unknown MIDI event type %i\n", event->event_type);
+            break;
+    }
+}
+
+static void ScheduleTrack(opl_track_data_t *track);
+
+// Restart a song from the beginning.
+
+static void RestartSong(void)
+{
+    unsigned int i;
+
+    running_tracks = num_tracks;
+
+    for (i=0; i<num_tracks; ++i)
+    {
+        MIDI_RestartIterator(tracks[i].iter);
+        ScheduleTrack(&tracks[i]);
+    }
+}
+
+// Callback function invoked when another event needs to be read from
+// a track.
+
+static void TrackTimerCallback(void *arg)
+{
+    opl_track_data_t *track = arg;
+    midi_event_t *event;
+
+    // Get the next event and process it.
+
+    if (!MIDI_GetNextEvent(track->iter, &event))
+    {
+        return;
+    }
+
+    ProcessEvent(track, event);
+
+    // End of track?
+
+    if (event->event_type == MIDI_EVENT_META
+     && event->data.meta.type == MIDI_META_END_OF_TRACK)
+    {
+        --running_tracks;
+
+        // When all tracks have finished, restart the song.
+
+        if (running_tracks <= 0 && song_looping)
+        {
+            RestartSong();
+        }
+
+        return;
+    }
+
+    // Reschedule the callback for the next event in the track.
+
+    ScheduleTrack(track);
+}
+
+static void ScheduleTrack(opl_track_data_t *track)
+{
+    unsigned int nticks;
+    unsigned int ms;
+    static int total = 0;
+
+    // Get the number of milliseconds until the next event.
+
+    nticks = MIDI_GetDeltaTime(track->iter);
+    ms = (nticks * track->ms_per_beat) / track->ticks_per_beat;
+    total += ms;
+
+    // Set a timer to be invoked when the next event is
+    // ready to play.
+
+    OPL_SetCallback(ms, TrackTimerCallback, track);
+}
+
+// Initialize a channel.
+
+static void InitChannel(opl_track_data_t *track, opl_channel_data_t *channel)
+{
+    // TODO: Work out sensible defaults?
+
+    channel->instrument = &main_instrs[0];
+    channel->volume = 127;
+    channel->bend = 0;
+}
+
+// Start a MIDI track playing:
+
+static void StartTrack(midi_file_t *file, unsigned int track_num)
+{
+    opl_track_data_t *track;
+    unsigned int i;
+
+    track = &tracks[track_num];
+    track->iter = MIDI_IterateTrack(file, track_num);
+    track->ticks_per_beat = MIDI_GetFileTimeDivision(file);
+
+    // Default is 120 bpm.
+    // TODO: this is wrong
+
+    track->ms_per_beat = 500 * 260;
+
+    for (i=0; i<MIDI_CHANNELS_PER_TRACK; ++i)
+    {
+        InitChannel(track, &track->channels[i]);
+    }
+
+    // Schedule the first event.
+
+    ScheduleTrack(track);
+}
+
+// Start playing a mid
+
+static void I_OPL_PlaySong(void *handle, int looping)
+{
+    midi_file_t *file;
+    unsigned int i;
+
+    if (!music_initialized || handle == NULL)
+    {
+        return;
+    }
+
+    file = handle;
+
+    // Allocate track data.
+
+    tracks = malloc(MIDI_NumTracks(file) * sizeof(opl_track_data_t));
+
+    num_tracks = MIDI_NumTracks(file);
+    running_tracks = num_tracks;
+    song_looping = looping;
+
+    for (i=0; i<num_tracks; ++i)
+    {
+        StartTrack(file, i);
+    }
+}
+
+static void I_OPL_PauseSong(void)
+{
+    unsigned int i;
+
+    if (!music_initialized)
+    {
+        return;
+    }
+
+    // Pause OPL callbacks.
+
+    OPL_SetPaused(1);
+
+    // Turn off all main instrument voices (not percussion).
+    // This is what Vanilla does.
+
+    for (i=0; i<OPL_NUM_VOICES; ++i)
+    {
+        if (voices[i].channel != NULL
+         && voices[i].current_instr < percussion_instrs)
+        {
+            VoiceKeyOff(&voices[i]);
+        }
+    }
+}
+
+static void I_OPL_ResumeSong(void)
+{
+    if (!music_initialized)
+    {
+        return;
+    }
+
+    OPL_SetPaused(0);
+}
+
+static void I_OPL_StopSong(void)
+{
+    unsigned int i;
+
+    if (!music_initialized)
+    {
+        return;
+    }
+
+    OPL_Lock();
+
+    // Stop all playback.
+
+    OPL_ClearCallbacks();
+
+    // Free all voices.
+
+    for (i=0; i<OPL_NUM_VOICES; ++i)
+    {
+        if (voices[i].channel != NULL)
+        {
+            VoiceKeyOff(&voices[i]);
+            ReleaseVoice(&voices[i]);
+        }
+    }
+
+    // Free all track data.
+
+    for (i=0; i<num_tracks; ++i)
+    {
+        MIDI_FreeIterator(tracks[i].iter);
+    }
+
+    free(tracks);
+
+    tracks = NULL;
+    num_tracks = 0;
+
+    OPL_Unlock();
+}
+
+static void I_OPL_UnRegisterSong(void *handle)
+{
+    if (!music_initialized)
+    {
+        return;
+    }
+
+    if (handle != NULL)
+    {
+        MIDI_FreeFile(handle);
+    }
+}
+
+// Determine whether memory block is a .mid file 
+
+static boolean IsMid(byte *mem, int len)
+{
+    return len > 4 && !memcmp(mem, "MThd", 4);
+}
+
+static boolean ConvertMus(byte *musdata, int len, char *filename)
+{
+    MEMFILE *instream;
+    MEMFILE *outstream;
+    void *outbuf;
+    size_t outbuf_len;
+    int result;
+
+    instream = mem_fopen_read(musdata, len);
+    outstream = mem_fopen_write();
+
+    result = mus2mid(instream, outstream);
+
+    if (result == 0)
+    {
+        mem_get_buf(outstream, &outbuf, &outbuf_len);
+
+        M_WriteFile(filename, outbuf, outbuf_len);
+    }
+
+    mem_fclose(instream);
+    mem_fclose(outstream);
+
+    return result;
+}
+
+static void *I_OPL_RegisterSong(void *data, int len)
+{
+    midi_file_t *result;
+    char *filename;
+
+    if (!music_initialized)
+    {
+        return NULL;
+    }
+
+    // MUS files begin with "MUS"
+    // Reject anything which doesnt have this signature
+
+    filename = M_TempFile("doom.mid");
+
+    if (IsMid(data, len) && len < MAXMIDLENGTH)
+    {
+        M_WriteFile(filename, data, len);
+    }
+    else 
+    {
+	// Assume a MUS file and try to convert
+
+        ConvertMus(data, len, filename);
+    }
+
+    result = MIDI_LoadFile(filename);
+
+    if (result == NULL)
+    {
+        fprintf(stderr, "I_OPL_RegisterSong: Failed to load MID.\n");
+    }
+
+    // remove file now
+
+    remove(filename);
+
+    Z_Free(filename);
+
+    return result;
+}
+
+// Is the song playing?
+
+static boolean I_OPL_MusicIsPlaying(void)
+{
+    if (!music_initialized)
+    {
+        return false;
+    }
+
+    return num_tracks > 0;
+}
+
+// Shutdown music
+
+static void I_OPL_ShutdownMusic(void)
+{
+    if (music_initialized)
+    {
+        // Stop currently-playing track, if there is one:
+
+        I_OPL_StopSong();
+
+        OPL_Shutdown();
+
+        // Release GENMIDI lump
+
+        W_ReleaseLumpName("GENMIDI");
+
+        music_initialized = false;
+    }
+}
+
+// Initialize music subsystem
+
+static boolean I_OPL_InitMusic(void)
+{
+    OPL_SetSampleRate(snd_samplerate);
+
+    if (!OPL_Init(opl_io_port))
+    {
+        printf("Dude.  The Adlib isn't responding.\n");
+        return false;
+    }
+
+    // Load instruments from GENMIDI lump:
+
+    if (!LoadInstrumentTable())
+    {
+        OPL_Shutdown();
+        return false;
+    }
+
+    InitVoices();
+
+    tracks = NULL;
+    num_tracks = 0;
+    music_initialized = true;
+
+    return true;
+}
+
+static snddevice_t music_opl_devices[] =
+{
+    SNDDEVICE_ADLIB,
+    SNDDEVICE_SB,
+};
+
+music_module_t music_opl_module =
+{
+    music_opl_devices,
+    arrlen(music_opl_devices),
+    I_OPL_InitMusic,
+    I_OPL_ShutdownMusic,
+    I_OPL_SetMusicVolume,
+    I_OPL_PauseSong,
+    I_OPL_ResumeSong,
+    I_OPL_RegisterSong,
+    I_OPL_UnRegisterSong,
+    I_OPL_PlaySong,
+    I_OPL_StopSong,
+    I_OPL_MusicIsPlaying,
+};
+
diff --git a/src/i_sdlmusic.c b/src/i_sdlmusic.c
index 7f9bd8ec..4aa89add 100644
--- a/src/i_sdlmusic.c
+++ b/src/i_sdlmusic.c
@@ -334,8 +334,6 @@ static boolean I_SDL_MusicIsPlaying(void)
 
 static snddevice_t music_sdl_devices[] =
 {
-    SNDDEVICE_ADLIB,
-    SNDDEVICE_SB,
     SNDDEVICE_PAS,
     SNDDEVICE_GUS,
     SNDDEVICE_WAVEBLASTER,
diff --git a/src/midifile.c b/src/midifile.c
new file mode 100644
index 00000000..bd935ca1
--- /dev/null
+++ b/src/midifile.c
@@ -0,0 +1,815 @@
+// Emacs style mode select   -*- C++ -*- 
+//-----------------------------------------------------------------------------
+//
+// Copyright(C) 2009 Simon Howard
+//
+// This program is free software; you can redistribute it and/or
+// modify it under the terms of the GNU General Public License
+// as published by the Free Software Foundation; either version 2
+// of the License, or (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with this program; if not, write to the Free Software
+// Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
+// 02111-1307, USA.
+//
+// DESCRIPTION:
+//    Reading of MIDI files.
+//
+//-----------------------------------------------------------------------------
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <assert.h>
+
+#include "doomdef.h"
+#include "doomtype.h"
+#include "i_swap.h"
+#include "midifile.h"
+
+#define HEADER_CHUNK_ID "MThd"
+#define TRACK_CHUNK_ID  "MTrk"
+#define MAX_BUFFER_SIZE 0x10000
+
+typedef struct
+{
+    byte chunk_id[4];
+    unsigned int chunk_size;
+} PACKEDATTR chunk_header_t;
+
+typedef struct
+{
+    chunk_header_t chunk_header;
+    unsigned short format_type;
+    unsigned short num_tracks;
+    unsigned short time_division;
+} PACKEDATTR midi_header_t;
+
+typedef struct
+{
+    // Length in bytes:
+
+    unsigned int data_len;
+
+    // Events in this track:
+
+    midi_event_t *events;
+    int num_events;
+} midi_track_t;
+
+struct midi_track_iter_s
+{
+    midi_track_t *track;
+    unsigned int position;
+};
+
+struct midi_file_s
+{
+    midi_header_t header;
+
+    // All tracks in this file:
+    midi_track_t *tracks;
+    unsigned int num_tracks;
+
+    // Data buffer used to store data read for SysEx or meta events:
+    byte *buffer;
+    unsigned int buffer_size;
+};
+
+// Check the header of a chunk:
+
+static boolean CheckChunkHeader(chunk_header_t *chunk,
+                                char *expected_id)
+{
+    boolean result;
+    
+    result = (memcmp((char *) chunk->chunk_id, expected_id, 4) == 0);
+
+    if (!result)
+    {
+        fprintf(stderr, "CheckChunkHeader: Expected '%s' chunk header, "
+                        "got '%c%c%c%c'\n",
+                        expected_id,
+                        chunk->chunk_id[0], chunk->chunk_id[1],
+                        chunk->chunk_id[2], chunk->chunk_id[3]);
+    }
+
+    return result;
+}
+
+// Read a single byte.  Returns false on error.
+
+static boolean ReadByte(byte *result, FILE *stream)
+{
+    int c;
+
+    c = fgetc(stream);
+
+    if (c == EOF)
+    {
+        fprintf(stderr, "ReadByte: Unexpected end of file\n");
+        return false;
+    }
+    else
+    {
+        *result = (byte) c;
+
+        return true;
+    }
+}
+
+// Read a variable-length value.
+
+static boolean ReadVariableLength(unsigned int *result, FILE *stream)
+{
+    int i;
+    byte b;
+
+    *result = 0;
+
+    for (i=0; i<4; ++i)
+    {
+        if (!ReadByte(&b, stream))
+        {
+            fprintf(stderr, "ReadVariableLength: Error while reading "
+                            "variable-length value\n");
+            return false;
+        }
+
+        // Insert the bottom seven bits from this byte.
+
+        *result <<= 7;
+        *result |= b & 0x7f;
+
+        // If the top bit is not set, this is the end.
+
+        if ((b & 0x80) == 0)
+        {
+            return true;
+        }
+    }
+
+    fprintf(stderr, "ReadVariableLength: Variable-length value too "
+                    "long: maximum of four bytes\n");
+    return false;
+}
+
+// Read a byte sequence into the data buffer.
+
+static void *ReadByteSequence(unsigned int num_bytes, FILE *stream)
+{
+    unsigned int i;
+    byte *result;
+
+    // Allocate a buffer:
+
+    result = malloc(num_bytes);
+
+    if (result == NULL)
+    {
+        fprintf(stderr, "ReadByteSequence: Failed to allocate buffer\n");
+        return NULL;
+    }
+
+    // Read the data:
+
+    for (i=0; i<num_bytes; ++i)
+    {
+        if (!ReadByte(&result[i], stream))
+        {
+            fprintf(stderr, "ReadByteSequence: Error while reading byte %u\n",
+                            i);
+            free(result);
+            return NULL;
+        }
+    }
+
+    return result;
+}
+
+// Read a MIDI channel event.
+// two_param indicates that the event type takes two parameters
+// (three byte) otherwise it is single parameter (two byte)
+
+static boolean ReadChannelEvent(midi_event_t *event,
+                                byte event_type, boolean two_param,
+                                FILE *stream)
+{
+    byte b;
+
+    // Set basics:
+
+    event->event_type = event_type & 0xf0;
+    event->data.channel.channel = event_type & 0x0f;
+
+    // Read parameters:
+
+    if (!ReadByte(&b, stream))
+    {
+        fprintf(stderr, "ReadChannelEvent: Error while reading channel "
+                        "event parameters\n");
+        return false;
+    }
+
+    event->data.channel.param1 = b;
+
+    // Second parameter:
+
+    if (two_param)
+    {
+        if (!ReadByte(&b, stream))
+        {
+            fprintf(stderr, "ReadChannelEvent: Error while reading channel "
+                            "event parameters\n");
+            return false;
+        }
+
+        event->data.channel.param2 = b;
+    }
+
+    return true;
+}
+
+// Read sysex event:
+
+static boolean ReadSysExEvent(midi_event_t *event, int event_type,
+                              FILE *stream)
+{
+    event->event_type = event_type;
+
+    if (!ReadVariableLength(&event->data.sysex.length, stream))
+    {
+        fprintf(stderr, "ReadSysExEvent: Failed to read length of "
+                                        "SysEx block\n");
+        return false;
+    }
+
+    // Read the byte sequence:
+
+    event->data.sysex.data = ReadByteSequence(event->data.sysex.length, stream);
+
+    if (event->data.sysex.data == NULL)
+    {
+        fprintf(stderr, "ReadSysExEvent: Failed while reading SysEx event\n");
+        return false;
+    }
+
+    return true;
+}
+
+// Read meta event:
+
+static boolean ReadMetaEvent(midi_event_t *event, FILE *stream)
+{
+    byte b;
+
+    event->event_type = MIDI_EVENT_META;
+
+    // Read meta event type:
+
+    if (!ReadByte(&b, stream))
+    {
+        fprintf(stderr, "ReadMetaEvent: Failed to read meta event type\n");
+        return false;
+    }
+
+    event->data.meta.type = b;
+
+    // Read length of meta event data:
+
+    if (!ReadVariableLength(&event->data.meta.length, stream))
+    {
+        fprintf(stderr, "ReadSysExEvent: Failed to read length of "
+                                        "SysEx block\n");
+        return false;
+    }
+
+    // Read the byte sequence:
+
+    event->data.meta.data = ReadByteSequence(event->data.meta.length, stream);
+
+    if (event->data.meta.data == NULL)
+    {
+        fprintf(stderr, "ReadSysExEvent: Failed while reading SysEx event\n");
+        return false;
+    }
+
+    return true;
+}
+
+static boolean ReadEvent(midi_event_t *event, unsigned int *last_event_type,
+                         FILE *stream)
+{
+    byte event_type;
+
+    if (!ReadVariableLength(&event->delta_time, stream))
+    {
+        fprintf(stderr, "ReadEvent: Failed to read event timestamp\n");
+        return false;
+    }
+
+    if (!ReadByte(&event_type, stream))
+    {
+        fprintf(stderr, "ReadEvent: Failed to read event type\n");
+        return false;
+    }
+
+    // All event types have their top bit set.  Therefore, if 
+    // the top bit is not set, it is because we are using the "same
+    // as previous event type" shortcut to save a byte.  Skip back
+    // a byte so that we read this byte again.
+
+    if ((event_type & 0x80) == 0)
+    {
+        event_type = *last_event_type;
+
+        if (fseek(stream, -1, SEEK_CUR) < 0)
+        {
+            fprintf(stderr, "ReadEvent: Unable to seek in stream\n");
+            return false;
+        }
+    }
+    else
+    {
+        *last_event_type = event_type;
+    }
+
+    // Check event type:
+
+    switch (event_type & 0xf0)
+    {
+        // Two parameter channel events:
+
+        case MIDI_EVENT_NOTE_OFF:
+        case MIDI_EVENT_NOTE_ON:
+        case MIDI_EVENT_AFTERTOUCH:
+        case MIDI_EVENT_CONTROLLER:
+        case MIDI_EVENT_PITCH_BEND:
+            return ReadChannelEvent(event, event_type, true, stream);
+
+        // Single parameter channel events:
+
+        case MIDI_EVENT_PROGRAM_CHANGE:
+        case MIDI_EVENT_CHAN_AFTERTOUCH:
+            return ReadChannelEvent(event, event_type, false, stream);
+
+        default:
+            break;
+    }
+
+    // Specific value?
+
+    switch (event_type)
+    {
+        case MIDI_EVENT_SYSEX:
+        case MIDI_EVENT_SYSEX_SPLIT:
+            return ReadSysExEvent(event, event_type, stream);
+
+        case MIDI_EVENT_META:
+            return ReadMetaEvent(event, stream);
+
+        default:
+            break;
+    }
+
+    fprintf(stderr, "ReadEvent: Unknown MIDI event type: 0x%x\n", event_type);
+    return false;
+}
+
+// Free an event:
+
+static void FreeEvent(midi_event_t *event)
+{
+    // Some event types have dynamically allocated buffers assigned
+    // to them that must be freed.
+
+    switch (event->event_type)
+    {
+        case MIDI_EVENT_SYSEX:
+        case MIDI_EVENT_SYSEX_SPLIT:
+            free(event->data.sysex.data);
+            break;
+
+        case MIDI_EVENT_META:
+            free(event->data.meta.data);
+            break;
+
+        default:
+            // Nothing to do.
+            break;
+    }
+}
+
+// Read and check the track chunk header
+
+static boolean ReadTrackHeader(midi_track_t *track, FILE *stream)
+{
+    size_t records_read;
+    chunk_header_t chunk_header;
+
+    records_read = fread(&chunk_header, sizeof(chunk_header_t), 1, stream);
+
+    if (records_read < 1)
+    {
+        return false;
+    }
+
+    if (!CheckChunkHeader(&chunk_header, TRACK_CHUNK_ID))
+    {
+        return false;
+    }
+
+    track->data_len = SDL_SwapBE32(chunk_header.chunk_size);
+
+    return true;
+}
+
+static boolean ReadTrack(midi_track_t *track, FILE *stream)
+{
+    midi_event_t *new_events;
+    midi_event_t *event;
+    unsigned int last_event_type;
+
+    track->num_events = 0;
+    track->events = NULL;
+
+    // Read the header:
+
+    if (!ReadTrackHeader(track, stream))
+    {
+        return false;
+    }
+
+    // Then the events:
+
+    last_event_type = 0;
+
+    for (;;)
+    {
+        // Resize the track slightly larger to hold another event:
+
+        new_events = realloc(track->events, 
+                             sizeof(midi_event_t) * (track->num_events + 1));
+
+        if (new_events == NULL)
+        {
+            return false;
+        }
+
+        track->events = new_events;
+
+        // Read the next event:
+
+        event = &track->events[track->num_events];
+        if (!ReadEvent(event, &last_event_type, stream))
+        {
+            return false;
+        }
+
+        ++track->num_events;
+
+        // End of track?
+
+        if (event->event_type == MIDI_EVENT_META
+         && event->data.meta.type == MIDI_META_END_OF_TRACK)
+        {
+            break;
+        }
+    }
+
+    return true;
+}
+
+// Free a track:
+
+static void FreeTrack(midi_track_t *track)
+{
+    unsigned int i;
+
+    for (i=0; i<track->num_events; ++i)
+    {
+        FreeEvent(&track->events[i]);
+    }
+
+    free(track->events);
+}
+
+static boolean ReadAllTracks(midi_file_t *file, FILE *stream)
+{
+    unsigned int i;
+
+    // Allocate list of tracks and read each track:
+
+    file->tracks = malloc(sizeof(midi_track_t) * file->num_tracks);
+
+    if (file->tracks == NULL)
+    {
+        return false;
+    }
+
+    memset(file->tracks, 0, sizeof(midi_track_t) * file->num_tracks);
+
+    // Read each track:
+
+    for (i=0; i<file->num_tracks; ++i)
+    {
+        if (!ReadTrack(&file->tracks[i], stream))
+        {
+            return false;
+        }
+    }
+
+    return true;
+}
+
+// Read and check the header chunk.
+
+static boolean ReadFileHeader(midi_file_t *file, FILE *stream)
+{
+    size_t records_read;
+    unsigned int format_type;
+
+    records_read = fread(&file->header, sizeof(midi_header_t), 1, stream);
+
+    if (records_read < 1)
+    {
+        return false;
+    }
+
+    if (!CheckChunkHeader(&file->header.chunk_header, HEADER_CHUNK_ID)
+     || SDL_SwapBE32(file->header.chunk_header.chunk_size) != 6)
+    {
+        fprintf(stderr, "ReadFileHeader: Invalid MIDI chunk header! "
+                        "chunk_size=%i\n",
+                        SDL_SwapBE32(file->header.chunk_header.chunk_size));
+        return false;
+    }
+
+    format_type = SDL_SwapBE16(file->header.format_type);
+    file->num_tracks = SDL_SwapBE16(file->header.num_tracks);
+
+    if ((format_type != 0 && format_type != 1)
+     || file->num_tracks < 1)
+    {
+        fprintf(stderr, "ReadFileHeader: Only type 0/1 "
+                                         "MIDI files supported!\n");
+        return false;
+    }
+
+    return true;
+}
+
+void MIDI_FreeFile(midi_file_t *file)
+{
+    int i;
+
+    if (file->tracks != NULL)
+    {
+        for (i=0; i<file->num_tracks; ++i)
+        {
+            FreeTrack(&file->tracks[i]);
+        }
+
+        free(file->tracks);
+    }
+
+    free(file);
+}
+
+midi_file_t *MIDI_LoadFile(char *filename)
+{
+    midi_file_t *file;
+    FILE *stream;
+
+    file = malloc(sizeof(midi_file_t));
+
+    if (file == NULL)
+    {
+        return NULL;
+    }
+
+    file->tracks = NULL;
+    file->num_tracks = 0;
+    file->buffer = NULL;
+    file->buffer_size = 0;
+
+    // Open file
+
+    stream = fopen(filename, "rb");
+
+    if (stream == NULL)
+    {
+        fprintf(stderr, "MIDI_LoadFile: Failed to open '%s'\n", filename);
+        MIDI_FreeFile(file);
+        return NULL;
+    }
+
+    // Read MIDI file header
+
+    if (!ReadFileHeader(file, stream))
+    {
+        fclose(stream);
+        MIDI_FreeFile(file);
+        return NULL;
+    }
+
+    // Read all tracks:
+
+    if (!ReadAllTracks(file, stream))
+    {
+        fclose(stream);
+        MIDI_FreeFile(file);
+        return NULL;
+    }
+
+    fclose(stream);
+
+    return file;
+}
+
+// Get the number of tracks in a MIDI file.
+
+unsigned int MIDI_NumTracks(midi_file_t *file)
+{
+    return file->num_tracks;
+}
+
+// Start iterating over the events in a track.
+
+midi_track_iter_t *MIDI_IterateTrack(midi_file_t *file, unsigned int track)
+{
+    midi_track_iter_t *iter;
+
+    assert(track < file->num_tracks);
+
+    iter = malloc(sizeof(*iter));
+    iter->track = &file->tracks[track];
+    iter->position = 0;
+
+    return iter;
+}
+
+void MIDI_FreeIterator(midi_track_iter_t *iter)
+{
+    free(iter);
+}
+
+// Get the time until the next MIDI event in a track.
+
+unsigned int MIDI_GetDeltaTime(midi_track_iter_t *iter)
+{
+    if (iter->position < iter->track->num_events)
+    {
+        midi_event_t *next_event;
+
+        next_event = &iter->track->events[iter->position];
+
+        return next_event->delta_time;
+    }
+    else
+    {
+        return 0;
+    }
+}
+
+// Get a pointer to the next MIDI event.
+
+int MIDI_GetNextEvent(midi_track_iter_t *iter, midi_event_t **event)
+{
+    if (iter->position < iter->track->num_events)
+    {
+        *event = &iter->track->events[iter->position];
+        ++iter->position;
+
+        return 1;
+    }
+    else
+    {
+        return 0;
+    }
+}
+
+unsigned int MIDI_GetFileTimeDivision(midi_file_t *file)
+{
+    return file->header.time_division;
+}
+
+void MIDI_RestartIterator(midi_track_iter_t *iter)
+{
+    iter->position = 0;
+}
+
+#ifdef TEST
+
+static char *MIDI_EventTypeToString(midi_event_type_t event_type)
+{
+    switch (event_type)
+    {
+        case MIDI_EVENT_NOTE_OFF:
+            return "MIDI_EVENT_NOTE_OFF";
+        case MIDI_EVENT_NOTE_ON:
+            return "MIDI_EVENT_NOTE_ON";
+        case MIDI_EVENT_AFTERTOUCH:
+            return "MIDI_EVENT_AFTERTOUCH";
+        case MIDI_EVENT_CONTROLLER:
+            return "MIDI_EVENT_CONTROLLER";
+        case MIDI_EVENT_PROGRAM_CHANGE:
+            return "MIDI_EVENT_PROGRAM_CHANGE";
+        case MIDI_EVENT_CHAN_AFTERTOUCH:
+            return "MIDI_EVENT_CHAN_AFTERTOUCH";
+        case MIDI_EVENT_PITCH_BEND:
+            return "MIDI_EVENT_PITCH_BEND";
+        case MIDI_EVENT_SYSEX:
+            return "MIDI_EVENT_SYSEX";
+        case MIDI_EVENT_SYSEX_SPLIT:
+            return "MIDI_EVENT_SYSEX_SPLIT";
+        case MIDI_EVENT_META:
+            return "MIDI_EVENT_META";
+
+        default:
+            return "(unknown)";
+    }
+}
+
+void PrintTrack(midi_track_t *track)
+{
+    midi_event_t *event;
+    unsigned int i;
+
+    for (i=0; i<track->num_events; ++i)
+    {
+        event = &track->events[i];
+
+        if (event->delta_time > 0)
+        {
+            printf("Delay: %i ticks\n", event->delta_time);
+        }
+
+        printf("Event type: %s (%i)\n",
+               MIDI_EventTypeToString(event->event_type),
+               event->event_type);
+
+        switch(event->event_type)
+        {
+            case MIDI_EVENT_NOTE_OFF:
+            case MIDI_EVENT_NOTE_ON:
+            case MIDI_EVENT_AFTERTOUCH:
+            case MIDI_EVENT_CONTROLLER:
+            case MIDI_EVENT_PROGRAM_CHANGE:
+            case MIDI_EVENT_CHAN_AFTERTOUCH:
+            case MIDI_EVENT_PITCH_BEND:
+                printf("\tChannel: %i\n", event->data.channel.channel);
+                printf("\tParameter 1: %i\n", event->data.channel.param1);
+                printf("\tParameter 2: %i\n", event->data.channel.param2);
+                break;
+
+            case MIDI_EVENT_SYSEX:
+            case MIDI_EVENT_SYSEX_SPLIT:
+                printf("\tLength: %i\n", event->data.sysex.length);
+                break;
+
+            case MIDI_EVENT_META:
+                printf("\tMeta type: %i\n", event->data.meta.type);
+                printf("\tLength: %i\n", event->data.meta.length);
+                break;
+        }
+    }
+}
+
+int main(int argc, char *argv[])
+{
+    midi_file_t *file;
+    unsigned int i;
+
+    if (argc < 2)
+    {
+        printf("Usage: %s <filename>\n", argv[0]);
+        exit(1);
+    }
+
+    file = MIDI_LoadFile(argv[1]);
+
+    if (file == NULL)
+    {
+        fprintf(stderr, "Failed to open %s\n", argv[1]);
+        exit(1);
+    }
+
+    for (i=0; i<file->num_tracks; ++i)
+    {
+        printf("\n== Track %i ==\n\n", i);
+
+        PrintTrack(&file->tracks[i]);
+    }
+
+    return 0;
+}
+
+#endif
+
diff --git a/src/midifile.h b/src/midifile.h
new file mode 100644
index 00000000..4ee0ddb2
--- /dev/null
+++ b/src/midifile.h
@@ -0,0 +1,175 @@
+// Emacs style mode select   -*- C++ -*- 
+//-----------------------------------------------------------------------------
+//
+// Copyright(C) 2009 Simon Howard
+//
+// This program is free software; you can redistribute it and/or
+// modify it under the terms of the GNU General Public License
+// as published by the Free Software Foundation; either version 2
+// of the License, or (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with this program; if not, write to the Free Software
+// Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
+// 02111-1307, USA.
+//
+// DESCRIPTION:
+//     MIDI file parsing.
+//
+//-----------------------------------------------------------------------------
+
+#ifndef MIDIFILE_H
+#define MIDIFILE_H
+
+typedef struct midi_file_s midi_file_t;
+typedef struct midi_track_iter_s midi_track_iter_t;
+
+#define MIDI_CHANNELS_PER_TRACK 16
+
+typedef enum
+{
+    MIDI_EVENT_NOTE_OFF        = 0x80,
+    MIDI_EVENT_NOTE_ON         = 0x90,
+    MIDI_EVENT_AFTERTOUCH      = 0xa0,
+    MIDI_EVENT_CONTROLLER      = 0xb0,
+    MIDI_EVENT_PROGRAM_CHANGE  = 0xc0,
+    MIDI_EVENT_CHAN_AFTERTOUCH = 0xd0,
+    MIDI_EVENT_PITCH_BEND      = 0xe0,
+
+    MIDI_EVENT_SYSEX           = 0xf0,
+    MIDI_EVENT_SYSEX_SPLIT     = 0xf7,
+    MIDI_EVENT_META            = 0xff,
+} midi_event_type_t;
+
+typedef enum
+{
+    MIDI_CONTROLLER_BANK_SELECT     = 0x0,
+    MIDI_CONTROLLER_MODULATION      = 0x1,
+    MIDI_CONTROLLER_BREATH_CONTROL  = 0x2,
+    MIDI_CONTROLLER_FOOT_CONTROL    = 0x3,
+    MIDI_CONTROLLER_PORTAMENTO      = 0x4,
+    MIDI_CONTROLLER_DATA_ENTRY      = 0x5,
+
+    MIDI_CONTROLLER_MAIN_VOLUME     = 0x7,
+    MIDI_CONTROLLER_PAN             = 0xa
+} midi_controller_t;
+
+typedef enum
+{
+    MIDI_META_SEQUENCE_NUMBER       = 0x0,
+
+    MIDI_META_TEXT                  = 0x1,
+    MIDI_META_COPYRIGHT             = 0x2,
+    MIDI_META_TRACK_NAME            = 0x3,
+    MIDI_META_INSTR_NAME            = 0x4,
+    MIDI_META_LYRICS                = 0x5,
+    MIDI_META_MARKER                = 0x6,
+    MIDI_META_CUE_POINT             = 0x7,
+
+    MIDI_META_CHANNEL_PREFIX        = 0x20,
+    MIDI_META_END_OF_TRACK          = 0x2f,
+
+    MIDI_META_SET_TEMPO             = 0x51,
+    MIDI_META_SMPTE_OFFSET          = 0x54,
+    MIDI_META_TIME_SIGNATURE        = 0x58,
+    MIDI_META_KEY_SIGNATURE         = 0x59,
+    MIDI_META_SEQUENCER_SPECIFIC    = 0x7f,
+} midi_meta_event_type_t;
+
+typedef struct
+{
+    // Meta event type:
+
+    unsigned int type;
+
+    // Length:
+
+    unsigned int length;
+
+    // Meta event data:
+
+    byte *data;
+} midi_meta_event_data_t;
+
+typedef struct
+{
+    // Length:
+
+    unsigned int length;
+
+    // Event data:
+
+    byte *data;
+} midi_sysex_event_data_t;
+
+typedef struct
+{
+    // The channel number to which this applies:
+
+    unsigned int channel;
+
+    // Extra parameters:
+
+    unsigned int param1;
+    unsigned int param2;
+} midi_channel_event_data_t;
+
+typedef struct
+{
+    // Time between the previous event and this event.
+    unsigned int delta_time;
+
+    // Type of event:
+    midi_event_type_t event_type;
+
+    union
+    {
+        midi_channel_event_data_t channel;
+        midi_meta_event_data_t meta;
+        midi_sysex_event_data_t sysex;
+    } data;
+} midi_event_t;
+
+// Load a MIDI file.
+
+midi_file_t *MIDI_LoadFile(char *filename);
+
+// Free a MIDI file.
+
+void MIDI_FreeFile(midi_file_t *file);
+
+// Get the time division value from the MIDI header.
+
+unsigned int MIDI_GetFileTimeDivision(midi_file_t *file);
+
+// Get the number of tracks in a MIDI file.
+
+unsigned int MIDI_NumTracks(midi_file_t *file);
+
+// Start iterating over the events in a track.
+
+midi_track_iter_t *MIDI_IterateTrack(midi_file_t *file, unsigned int track_num);
+
+// Free an iterator.
+
+void MIDI_FreeIterator(midi_track_iter_t *iter);
+
+// Get the time until the next MIDI event in a track.
+
+unsigned int MIDI_GetDeltaTime(midi_track_iter_t *iter);
+
+// Get a pointer to the next MIDI event.
+
+int MIDI_GetNextEvent(midi_track_iter_t *iter, midi_event_t **event);
+
+// Reset an iterator to the beginning of a track.
+
+void MIDI_RestartIterator(midi_track_iter_t *iter);
+
+#endif /* #ifndef MIDIFILE_H */
+
diff --git a/src/s_sound.c b/src/s_sound.c
index 1c56efb2..6c18f65e 100644
--- a/src/s_sound.c
+++ b/src/s_sound.c
@@ -128,6 +128,7 @@ int snd_sfxdevice = SNDDEVICE_SB;
 extern sound_module_t sound_sdl_module;
 extern sound_module_t sound_pcsound_module;
 extern music_module_t music_sdl_module;
+extern music_module_t music_opl_module;
 
 // Compiled-in sound modules:
 
@@ -146,6 +147,7 @@ static music_module_t *music_modules[] =
 {
 #ifdef FEATURE_SOUND
     &music_sdl_module,
+    &music_opl_module,
 #endif
     NULL,
 };
@@ -794,6 +796,15 @@ void S_ChangeMusic(int musicnum, int looping)
     char namebuf[9];
     void *handle;
 
+    // The Doom IWAD file has two versions of the intro music: d_intro
+    // and d_introa.  The latter is used for OPL playback.
+
+    if (musicnum == mus_intro && (snd_musicdevice == SNDDEVICE_ADLIB
+                               || snd_musicdevice == SNDDEVICE_SB))
+    {
+        musicnum = mus_introa;
+    }
+
     if (musicnum <= mus_None || musicnum >= NUMMUSIC)
     {
         I_Error("Bad music number %d", musicnum);