voice_sweep_frequency - Starts a frequency sweep for a voice. Allegro game programming library.

       Starts  a  frequency  sweep (glissando) from the current pitch to the specified ending pitch, lasting for
       time milliseconds.

       voice_sweep_frequency - Starts a frequency sweep for a voice. Allegro game programming library.

voice_set_frequency(3alleg4)

Allegro                                           version 4.4.3                   voice_sweep_frequency(3alleg4)

#include<allegro.h>voidvoice_sweep_frequency(intvoice,inttime,intendfreq);