al_set_sample_instance_speed - Allegro 5 API

       Set the relative playback speed of the sample instance.  1.0 means normal speed.

       Return  true  on  success,  false on failure.  Will fail if the sample instance is attached directly to a
       voice.

       al_set_sample_instance_speed - Allegro 5 API

al_get_sample_instance_speed(3alleg5)

Allegro reference manual                                                   al_set_sample_instance_speed(3alleg5)

              #include <allegro5/allegro_audio.h>

              bool al_set_sample_instance_speed(ALLEGRO_SAMPLE_INSTANCE *spl, float val)