Imuse is the system used for the music. It main feature is to allow perfect integration of the music; with some talent, the game music can appear as a continuous soundtrack to the player.

SCUMM interface

Imuse is a subsystem of the SCUMM engine with its own set of commands. From a SCUMM script the following functions are avaible:

startSound(snd)
stopSound(snd)
startMusic(m)
isSoundRunning(snd)
soundKludge([cmd_list])

As you can see, that is pretty spartan: all the power is in the soundKludge function. This will need some pretty good abstraction in the compiler, probably by adding a block similar to inline asm in C.

Command list

0x0006 : imSetMasterVolume(volume)
volume: [0-127]

0x0007 : imGetMasterVolume()

0x0008 : imStartSound(sound)

0x0009 : imStopSound(sound)

0x000A : imStopAllSounds() ???

0x000B : imStopAllSounds()

0x000C : imPlayerSet(player, ???, cmd, params ...)
Used in S&M

0x000D : imGetSoundStatus(sound)
sound == -1 returns the first active sound

0x000E : imFadeSound(player, ????, fader_p1, fader_p2, fader_p3)
S&M only ?

0x000F : imMaybeHook(player, ????, param)
S&M

0x0010 : imSetVolchan(sound,volchan)

0x0011 : imSetChannelVolume(chan,volume)
In S&M: set/clear trigger

0x0012 : imSetVolchanEntry(volchan,val)
S&M: ImCheckTrigger

0x0013 : imClearTrigger(a,b)

0x0100 : imPlayerGetParam(player,param,chan)
In DOTT this is often called with only 2 args, in that case it seems to default to chan=0.
S&M: Beat suff

0x0101 : imPlayerSetPriority(player,prio)

0x0102 : imPlayerSetVolume(player,volume)
volume: [0:127]

0x0103 : imPlayerSetPan(player,pan)

0x0104 : imPlayerSetTranspose(player,relative,val)
val:[-24:24]

0x0105 : imPlayerSetDetune(player,detune)

0x0106 : imPlayerSetSpeed(player,speed)

0x0107 : imPlayerJump(player,track,beat,tick)

0x0108 : imPlayerScan(player,toTrack,toBeat,toTick)

0x0109 : imPlayerSetLoop(player,count,toBeat,toTick,fromBeat,fromTick)

0x010A : imPlayerClearLoop(player)

0x010B : imPlayerSetOnOff(player,chan,status)

0x010C : imPlayerSetHook(player,type,value,chan)

0x010D : imPlayerFade(player,target,time)

0x010E : imQueueTrigger(a,b)

0x010F : imQueueCommand(cmd,arg1,arg2,arg3,arg4,arg5,arg6)

0x0110 : imClearQueue()

0x0111 : ??? Live MIDI ON

0x0112 : ??? Live MIDI OFF

0x0113 : imPlayerGetParam(player,param,chan)

0x0114 : imPlayerSetHook(player,type,value,chan)

0x0115 : ???

0x0116 : imPlayerSetVolume(player,part,vol)

0x0117 : imQueryQueue(param)
param:
- 0: trigger count
- 1: last trigger type
- 2: last trigger sound

0x0118 : ???

Player parameters

0x00: priority
0x01: volume
0x02: pan
0x03: transpose
0x04: detune
0x05: speed
0x06: track index
0x07: beat index
0x08: tick index
0x09: loop counter
0x0A: loop to beat
0x0B: loop to tick
0x0C: loop from tick
0x0D: loop from tick
0x0E: part on
0x0F: part vol
0x10: part instrument
0x11: part transpose
0x12: jump hook
0x13: transpose hook
0x14: part onoff hook
0x15: part volume hook
0x16: part program hook
0x17: part transpose hook

Hook types

0x00: jump
0x01: transpose
0x02: chan on/off (0x0F == all)
0x03: chan volume (0x0F == all)
0x04: chan part program
0x05: chan transpose

MIDI SysEx

The MIDI data fed to iMUSE can contain (and to some extent needs) some special SysEx commands. The manufacturer ID 0x7D is used for these SysExes and the first byte indicates the command.

In the SysEx data, only the first 7 bits are significant (value in the 0x80-0xFF range are used for real-time messages among other things), so values larger than 7 bits use 1 nibble per byte in big endian order (most significant nibble first). In the following descriptions, each line corresponds to one or more bytes of data.

The relevant code in ScummVM 0.9 is in engines/scumm/imuse/sysex_scumm.cpp and engines/scumm/imuse/imuse_player.cpp.

0x00: Allocate new part

  part        : 4
  unknown     : 7
  flags       : 2 bit 0 turn the part on/off
                  bit 1 turn the reverb on/off
  priority    : 7
  volume      : 8
  pan         : 8
  flags2      : 7 bit 3 set percussion mode
  pitchbend   : 8
  program     : 8

0x01: Shut down a part

  part        : 4

0x02: Start of song
This command is ignored by ScummVM 0.9.
0x10: Adlib instrument definition (Part)

  part        : 4
  hw type     : 7
  adlib data  : 60*8

0x11: Adlib instrument definition (Global)

  unknown     : 7
  hw type     : 7
  intrument   : 7
  adlib data  : 60*8

0x21: Parameter adjust

  part        : 4
  hw type     : 7
  param       : 16be
  value       : 16be

0x30: Hook - jump

  unknown     : 7
  cmd         : 8
  track       : 16be
  beat        : 16be
  tick        : 16be

0x31: Hook - global transpose

  unknown     : 7
  cmd         : 8
  relative    : 8
  value       : s8

0x32: Hook - part on/off

  chan        : 4
  cmd         : 8
  value       : 8

0x33: Hook - set volume

  chan        : 4
  cmd         : 8
  value       : 8

0x34: Hook - set program

  chan        : 4
  cmd         : 8
  value       : 8

0x35: Hook - set transpose

  chan        : 4
  cmd         : 8
  relative    : 8
  value       : s8

0x40: Marker

  unknown     : 7
  marker      : 7*n

0x50: Set loop

  unknown     : 7
  count       : 16be
  tobeat      : 16be
  totick      : 16be
  frombeat    : 16be
  fromtick    : 16be

0x51: Clear loop
No arguments (or at least unused by ScummVM).
0x60: Set instrument

  chan        : 4
  instrument  : 16be

Adlib instrument

See some Adlib/Soundblaster documentation: http://www.shipbrook.com/jeff/sb.html

  operators             : 8*5*2
    characteristic      : 8 (port 0x20)
    scalingOutputLevel  : 8 (port 0x40)
    attackDecay         : 8 (port 0x60)
    sustainRelease      : 8 (port 0x80)
    waveformSelect      : 8 (port 0xE0)
  feedback              : 8 (port 0xC0)
  flags_a               : 8
  extra_a               : 8*8
  flags_b               : 8
  extra_b               : 8*8
  duration              : 8

Reference

http://alban.dotsec.net/Projects/Imuse

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ScummC internals