reallocate_voice man page
reallocate_voice — Switches the sample of an already-allocated voice. Allegro game programming library.
void reallocate_voice(int voice, const SAMPLE *spl);
Switches an already-allocated voice to use a different sample. Calling reallocate_voice(voice, sample) is equivalent to:
deallocate_voice(voice); voice = allocate_voice(sample);
allocate_voice(3), deallocate_voice(3), load_sample(3)