Music

Early v5

Going from Monkey Island 2 (MI2), music blocks are stored in LFLF blocks, outside of the ROOMs, so they can be accessed globally. The containing sound block looks like this:

Block name         4 bytes ("SOUN")
Block size         4 bytes
Block name         4 bytes ("SOU ")
Block size         4 bytes
Music block        variable

The redundant header is possibly due to building on a legacy implementation, or for easier identification in the table stored in the .000 index file.

The music block may contain any combination of ROL (Roland MT-32), ADL (Adlib/OPL FM), or SPK (PC speaker) blocks. They can also store a single SBL block for digitized sound (described in a later section). Aside from SBL, each of these blocks follow the same basic pattern.

 Block name        4 bytes ("ROL ", or "ADL ", or "SPK ")
 Block size        4 bytes
 MIDI data         variable

Every track is stored in MIDI format, in order to make use of the iMUSE technology through System Exclusive (SysEx) messages.

Due to the predominance of the Sound Blaster and Adlib/OPL FM technology at the time, in at least MI2 every musical SOUN block contains an ADL block.

iMUSE

From SCUMM v5 onwards, LucasArts games used a dynamic music playback system called iMUSE. This basically consists of standard MIDI data, with embedded System Exclusive (SysEx) messages that act as markers in the song. iMUSE allows operations like conditional jumping & looping, adjusting the volume of parts, turning parts on and off, changing instruments, and detuning parts.

You can find the original patent document here, and some technical details can be found here.

Mac0

From Markus Magnuson (superqult) we got this information:

   4 bytes - 'SOUN'
BE 4 bytes - block length

       4 bytes  - 'Mac0'
    BE 4 bytes  - (blockLength - 27)
       28 bytes - ???

       do this three times (once for each channel):
          4 bytes  - 'Chan'
       BE 4 bytes  - channel length
          4 bytes  - instrument name (e.g. 'MARI')

          do this for ((chanLength-24)/4) times:
             2 bytes  - note duration
             1 byte   - note value
             1 byte   - note velocity

          4 bytes - ???
          4 bytes - 'Loop'/'Done'
          4 bytes - ???
          1 byte - 0x09

Instruments (and General Midi equivalent):
       "MARI" - Marimba (12)
       "PLUC" - Pizzicato Strings (45)
       "HARM" - Harmonica (22)
       "PIPE" - Church Organ? (19) or Flute? (73) or Bag Pipe (109)
       "TROM" - Trombone (57)
       "STRI" - String Ensemble (48 or 49)
       "HORN" - French Horn? (60) or English Horn? (69)
       "VIBE" - Vibraphone (11)
       "SHAK" - Shakuhachi? (77)
       "PANP" - Pan Flute (75)
       "WHIS" - Whistle (78) / Bottle (76)
       "ORGA" - Drawbar Organ (16; but could also be 17-20)
       "BONG" - Woodblock? (115)
       "BASS" - Bass (32-39)

Digitized Sounds

Early v5 - SBL blocks

Digitized sounds first appeared in Monkey Island 1 & 2. They are contained in the .001 resource files, and are sub-blocks of "SOUN" blocks (see the music section above).

 Block name        4 bytes ("SBL ")
 Block size        4 bytes
 Sound header      4 bytes ("AUhd" or "WVhd")
 Unknown           3 bytes (always 00 00 80)
 Data header       4 bytes ("AUdt" or "WVdt")
 VOC data          variable

AUhd and AUdt are used in Monkey Island, while WVhd and WVdt are used in the non-interactive demo of Sam & Max. The actual sound data is stored in the Creative VOC format, without the identifying header.

Early v5 - CD tracks

Games that use CD tracks (Loom/CD, MI1/CD, Zak256/FM-TOWNS) are a bit different. For MI1/CD at least, the "SOU " block size is always 32 bytes and presumably points to the CD track to play.

v5-v6 - MONSTER.SOU

Original

From Indy 4 onwards, sound effects and speech are stored in a separate resource file called "MONSTER.SOU". The format is:

Block name         4 bytes ("SOU ")
Block size         4 bytes
One or more:
 Block name        4 bytes ("VCTL")
 Block size        4 bytes
 Lip-sync tags     variable
 Sound data        variable ("Crea" block / VOC file)

The lip-sync tags provide timing information. In v5 the number of tags is stored in the calling text, according to the formula ((num_tags / 2) << 1) + 8. The "Crea" block is an entire Creative VOC file.

Compressed

ScummVM can use compressed monster.sou files created with the tool "compress_scumm_sou.exe". Aside from using either MP3, OGG, or FLAC formats for the sound data, they contain a mapping table followed by the sound data, like so:

size_of_table  : uint32
size_of_table / 16 times {
 orig_offset   : uint32
 actual_offset : uint32
 num_tags      : uint32
 sound_size    : unit32
}
size_of_table / 16 times {
 num_tags times {
  tag          : uint8
 }
 sound         : sound_size (sound file - MP3/OGG/FLAC)
}

Each entry in the table has 4 items, each item is 4 bytes, so a table with one entry has a size of 16.

The original offset is what the game will try to play, the actual offset is taken from after the index table.

Each sound is directly preceded by its lip-synch tags.

Sound block types

This information is gleaned from the ScummVM source code. Any block name with only three characters has a space at the end.

MIDI \ Midi
iMUS /

SOU  subtypes
TOWS - FM Towns
SBL  - Sound Blaster digitized sound (Creative VOC file)
ADL  - Adlib (OPL FM)
AMI  - Amiga MOD
ROL  - Roland MT-32
GMD  - General MIDI
MAC  - Macintosh (occurs in MI2, FOA)
SPK  - PC speaker

Mac0 - Macintosh music type 0

Mac1 \
RIFF |
TALK  > Creative VOC file
DIGI |
Crea /

HSHD - HE sound type without SOUN header

FMUS - Used in 3DO versions of HE games

SCUMM/Technical Reference/Sound resources

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