reallocate_voice  -  Switches the sample of an already-allocated voice.
       Allegro game programming library.
       #include <allegro.h>
       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(3alleg), deallocate_voice(3alleg), load_sample(3alleg)