debian man page for set_hardware_volume

set_hardware_volume(3alleg4)					  Allegro manual				      set_hardware_volume(3alleg4)

NAME
       set_hardware_volume - Alters the hardware sound output volume. Allegro game programming library.

SYNOPSIS
       #include <allegro.h>

       void set_hardware_volume(int digi_volume, int midi_volume);

DESCRIPTION
       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.

SEE ALSO
       install_sound(3alleg4), set_volume(3alleg4)

Allegro 							   version 4.4.2				      set_hardware_volume(3alleg4)