Entry 26

Music and menu effects: a software SPU playing libsnd's songs

2026-10-1517maudio

The title had no music. The game's music is libsnd: SEP songs played through VAB banks on the SPU.

What the original does:

• A song set (0x8006e96c) names a music bank, an effects bank and a SEP. The menu's set is at 0x800b8030: MENU.VB/VH, banks 151/152, and RUGRATS.SEP with 5 songs.
• MidiPlaySong (0x8006eac4) plays a song. The title plays song 0 forever.
• The song volume (0x8006e74c) is the music setting, 90 at boot (read from the oracle's 0x800c5684).
• Effects (0x8006f26c) key on program, tone and note from the 180-entry table at 0x800b84fc. They play at the effects setting, 100, on voices 17-23 in turn.

The port:

• rugrats_data::sep reads SEP files.
• rugrats::sound::Spu plays them:
  • 24 voices with the SPU's ADSR (psx-spx rates) and rrt-kit's Gaussian interpolation.
  • A sequencer for note on/off, program, volume, pan, expression, pitch bend, tempo, libsnd's NRPN loop marks, and looping at the track end.
  • Effects keyed on the same way the game does.
• The audio device now plays Mix: the XA soundtrack plus the SPU.
• The title loads the menu set and plays song 0. Its menu sounds go to Spu::effect, and leaving for the demo stops the song.

Checks: song_wav renders song 0 for 30 s at peak 21990 and RMS 2859, with no clipping. Before the main volume (0x3fff) and the >> 15 voice volume were applied, it clipped.