Sound / Music

The audio engine: positional sound effects, threat-warning tones, ambient loops, and the two-layer music system — all driven onto the Miles Sound System (WAIL32.DLL / AIL) through a logical-voice mixer. 0x4328B0–0x435C60.

Provenance: Ghidra static analysis of the game executable with FA.SMS symbols applied; recorded in the symbol database and applied to the Ghidra project (five mixer functions folded into gaps — incl. the PollMod timer callback — are materialised on apply). Progress: reconstruction matrix. Markers follow spec-authoring.md: confirmed · inferred · unknown.

Logical voices onto physical channels

SoundOn (0x433680) is the master SFX entry — it parses the .11K/.XMI name, allocates a MODSPEC logical voice, and sets position/pitch/pan/falloff. There are 64 logical voices across four banks (_MOD, _pendMOD, _noMixLeft, _noMixRight) that multiplex onto 16 physical AIL sample handles:

SoundPrioritize resolves contention by priority voice-stealing, with a waiting queue (_pendMOD) drained by StartWaitingSounds. Two specializations: an 8-entry threat-warning tone table (_warnSnd: IR/radar tracking + lock, both directions) and looping ambients (_loopSnd: engine/wind/heartbeat, via MaybeLoopSound). The mixer is serviced by the 30 Hz timer callback PollMod. ServiceSounds runs per frame for per-object distance volume/pan; ViewPan computes stereo pan from a 3D point.

Music: dynamic score + shell

Two layers. Dynamic score (.MUS): ScoreOn loads a .MUS bytecode script and ScoreUpdate interprets it each frame (a byte-switch that weights and selects tracks), dispatching to MusicOn (XMIDI via AIL_*_sequence) or DMusicOn (digital .11K). See MUS.md. Shell music: ShellMusicUpdate picks menu / briefing / debrief tracks. The Miles driver is reached only through the _AIL_* import thunks; WAIL32.DLL itself is an overlay (out of scope here).

Functions

Full record: db/symbols/sound.csv.

VA	Symbol	Role
0x433180	InitSound	open the DIG_DRIVER; register the PollMod 30 Hz timer
0x433300	InitMixer	init 64 MODSPEC voices + the warn-tone table
0x433680	SoundOn	master SFX entry: allocate a voice, set 3D params
0x4349D0	ServiceSounds	per-frame per-object distance volume/pan
0x4354B0	PollMod	30 Hz AIL timer mixer-service callback
0x4357C0	SoundPrioritize	priority voice-stealing across 16 channels
0x435900	StartWaitingSounds	dequeue waiting voices when channels free
0x435980	StartVoice	AIL_start_sample on a physical channel
0x435A00	SetVolPitchPan	AIL 3D volume/pan/rate on a voice
0x4343B0	ViewPan	stereo pan from a 3D point vs the camera
0x432C30	ScoreOn	load a .MUS score
0x432CA0	ScoreUpdate	per-frame MUS bytecode interpreter
0x4329E0	MusicOn	start XMIDI playback
0x432F80	ShellMusicUpdate	pick menu/brief/debrief music

Open Questions

1. PollMod per-tick work — resolved

A fresh decompile shows PollMod (0x4354B0) is the pause/resume mixer service, not a voice-aging/fade stepper. Each tick it reconciles the mixer against the pause state (_timeCompression == 0x7FFF PAUSED, or MPPaused(), or DAT_004F3BC8):

• Music (when _musicOn): on entering pause it calls Miles AIL_stop_sequence on _musicSeqHandle (once, guarded by DAT_004F3BF0); on leaving pause, AIL_resume_sequence and restores volume via MusicVolume(_flightMusicVol) or MusicVolume(_otherMusicVol) depending on _curScreen.
• Sound (when _soundOn): on entering pause it silences all 16 voices — a loop over the _MOD voice table (stride 0x54) calling SetVolPitchPan(&_MOD[i], i) — guarded by DAT_004F3C08; it un-silences on resume.

So the per-tick work is suspend/restore of the Miles music sequence and the 16-voice _MOD table across pause transitions, plus screen-dependent music-volume selection.

Status: resolved — re-static (pause/resume of the Miles music sequence + 16-voice _MOD table).

Related

• formats/MUS.md — the .MUS score-bytecode format ScoreUpdate runs.
• formats/11K.md — the sampled-audio format.
• objects.md — ServiceSounds reads per-object state through the mirror.
• The Miles/AIL driver (WAIL32.DLL) — an overlay binary, tracked separately.