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musxplugin

Plays Acorn Archimedes Tracker modules (.musx) — the native format of Dan Wilson's !Tracker (1991), an Amiga-Soundtracker-style editor for the Acorn Archimedes that, unusually for its day, supported up to 8 channels with soft panning. Files begin with the ASCII magic MUSX and store IFF-style chunks (MNAM/ANAM title & author, MVOX channel count, PNUM/PATT patterns, up to 36 VIDC samples).

The "Archimedes ran on ARM, and we're on ARM" angle is a red herring: this is not native code emulation. The replayer is portable C — it runs the same on any host.

Engine: libxmp arch_loader

Playback uses libxmp's Archimedes Tracker loader (arch_load.c), which is already vendored in the tree under zxtune/3rdparty/xmp/. Rather than build the full ~58-format libxmp or depend on the shared zxtune libxmp target, this plugin compiles a minimal single-loader slice directly into libmusxplugin.a:

  • core libxmp (player/mixer/scan/effects/…) + loaders/{common,iff,sample, mmd_common,voltable,arch_load}.c
  • same trimmed build defines zxtune uses (NO_COMPOSITE_LOADER, NO_PROWIZARD, NO_EXTERNALFILES, DECRUNCH_MAX=0, …)
  • voltable.c is a required link dependency — it provides arch_vol_table, used by arch_load.c's get_samp().

It deliberately does not add_subdirectory() the shared zxtune/3rdparty/xmp build, so there is no duplicate xmp CMake target and chipmachine's zxtuneplugin is untouched.

The module is driven through libxmp's internal xmp_load_typed_module_from_memory(ctx, mem, size, &arch_loader) so only the Archimedes loader is ever tried — the public 58-format auto-detect table is never compiled in.

Routing

canHandle() accepts a file only when the extension is .musx and the first four bytes are MUSX. The .musx extension is also used by unrelated software (e.g. Finale notation), so the magic check keeps the plugin from grabbing foreign payloads. Because the gate is this narrow, there is no overlap with OpenMPT's Amiga/PC tracker formats.

getSamples() renders 16-bit signed stereo at 44100 Hz via xmp_play_buffer(..., loop=1) and returns -1 once the module has played through once, so the host advances instead of looping forever.

License

libxmp is MIT (zxtune/3rdparty/xmp/COPYING, © 1996–2024 Claudio Matsuoka and Hipolito Carraro Jr). The specific loader compiled here, arch_load.c, carries an LGPL-2.1-or-later header from its 2013 authorship. Either way it is redistributable with attribution; see the credits entry.

Tests

testmus/musx/ holds five Modland fixtures (varied authors and 4/8-channel tunes). Covered by TEST_CASE("Musx") (corpus scan) and TEST_CASE("Musx plays sound") (asserts non-silent output + magic gate) in chipmachine/test.cpp.