Music bank

The AMOS Music bank holds three independent sections: instruments (sample data), songs (per-channel pattern playlists), and patterns (per-voice note and command streams). Unlike ProTracker, the four voices are fully independent — there is no shared row grid.

Commands

# Export to JSON + WAV instrument samples
portamos disasm Music.Abk output/music.json

# Export with IFF 8SVX instrument samples
portamos disasm --8svx Music.Abk output/music.json

# Reassemble
portamos asm output/music.json Music.Abk

JSON schema

{
  "type": "Music",
  "bankNumber": 3,
  "chipRam": true,
  "instruments": [
    {
      "name": "Bass",
      "volume": 45,
      "loopStart": 112,
      "loopLength": 3247,
      "sample": "music-instrument000.wav"
    }
  ],
  "songs": [
    {
      "name": "My Song",
      "tempo": 15,
      "sequence": [
        [0, 1, 2, 65534],
        [0, 1, 2, 65534],
        [0, 1, 2, 65534],
        [0, 1, 2, 65534]
      ]
    }
  ],
  "patterns": [
    {
      "voices": [
        [
          { "command": "SET_INSTR", "parameter": 0 },
          { "period": 254, "duration": 16134 },
          { "period": 190, "duration": 16134 }
        ],
        [],
        [],
        []
      ]
    }
  ]
}

Field reference

Top level

Field	Type	Description
type	string	Always "Music"
bankNumber	integer	Bank slot (1-based)
chipRam	boolean	true = chip RAM, false = fast RAM

instruments[]

Field	Type	Description
name	string	Up to 16 ASCII characters
volume	integer	Default playback volume (0–63)
loopStart	integer	Byte offset within sample data where the loop starts (0 = no loop)
loopLength	integer	Loop length in 16-bit words (2 = no loop)
sample	string	Path to audio file relative to the JSON

Instrument samples are exported at their stored frequency (8363 Hz = Amiga standard). Actual pitch at runtime is determined by the note periods in the patterns.

songs[].sequence

Four per-channel playlists. Each is a list of 0-based pattern indices, terminated by:

• 65534 (0xFFFE) — loop back to the start of this channel’s playlist
• 65535 (0xFFFF) — stop playback on this channel

patterns[].voices

Four independent note streams. Each item is either:

Note:

{ "period": 254, "duration": 16134 }

Field	Type	Description
period	integer	Amiga hardware period (inversely proportional to pitch; 0 = silence)
duration	integer	Raw OldNote control word (bit 14 cleared); bits 13–8 = per-note volume (0–63), bits 7–0 = tick count

Command:

{ "command": "SET_VOLUME", "parameter": 48 }

Field	Type	Description
command	string	Command name (see list below)
parameter	integer	Command parameter (optional; 0 if omitted)

Command names

SET_VOLUME, STOP_EFFECT, REPEAT, FILTER_ON, FILTER_OFF, SET_TEMPO, SET_INSTR, ARPEGGIO, TONE_PORTAMENTO, VIBRATO, VOLUME_SLIDE, PORTAMENTO_UP, PORTAMENTO_DOWN, DELAY, POSITION_JUMP