set_hardware_volume - Alters the hardware sound output volume. Allegro game
programming library.
#include <allegro.h>
void set_hardware_volume(int digi_volume, int
midi_volume);
Alters the hardware sound output volume. Specify volumes for both digital
samples and MIDI playback, as integers from 0 to 255, or pass a negative value
to leave one of the settings unchanged. Values bigger than 255 will be reduced
to 255. This routine will use the hardware mixer to control the volume if it
exists (i.e. the volume of all the applications on your machine will be
affected), otherwise do nothing.
install_sound(3), set_volume(3)