Everything you hear here comes from running the cartridge's own sound engine (SUENA, 0x5D31, and SUENA_ESTO, 0x5C96, which hands it the channels; the interrupt calls it) on an emulated Z80, frame by frame at 60 per second, just as the game calls it. What the engine writes to the PSG is turned into sound with an AY-3-8910 (tools/musica.py). Each MP3 is the whole piece up to where it starts again, plus 8 seconds of the repeat fading out; those that do not repeat end where the engine ends.
The PSG writes have been compared frame by frame with those of openMSX (C-BIOS MSX1 japonés). In every frame the PSG ends up the same:
The timbre is not checked: it is a textbook AY-3-8910, not a recording of the emulator. The probes are tools/omsx_psg.tcl and tools/coteja_psg.py.
SUENA_ESTO takes the number in A. From 0x89 to 0x8C it uses two channels and from 0x8D up all three; below that, an effect on a single channel. The listing shows only two music requests, 0x89 and 0x8B; the rest of what the game asks for during play are effects (the engine hum, the shot, the bomb). Tracks 0x8A and 0x8C are in the track table but no routine asks for them with an ld a. The engine never writes the PSG mixer: ARRANCA_EL_SONIDO (0x47FC) sets it to 0xB8, and here it starts from that same value.
The demo fanfare (0x89)
Asked for by ESTADO_08_DEMO (0x47C1), antes de arrancar la demostración; lasts 4.3 s.
A short track in the table (0x8A)
Asked for by ninguna llamada directa: está en la tabla de pistas (0x5E5F); lasts 5.3 s.
The warning as the ship stops (0x8B)
Asked for by LA_NAVE_SE_PARA (0x509C) y MARCA_EL_TRAMO_FINAL (0x537D); lasts 5.3 s.
A long track in the table (0x8C)
Asked for by ninguna llamada directa: está en la tabla de pistas (0x5E5F); lasts 21.8 s.