I'm making a layered music, like
layer 1 = guitar
layer 2 = bass
layer 3 = drums.
All of them are same-length loops.
and all audio files are sync-ed with
audio_start_sync_group(group);
audio_sound_gain(guitar,0,0);
audio_sound_gain(bass,0,0);
audio_sound_gain(drums,1,0);
in the creation code...