set_audio
set_audio( bktr, AUDIO_MUTE ); /* prevent 'click' */
set_audio( bktr, AUDIO_UNMUTE );
int set_audio( bktr_ptr_t bktr, int mode );
set_audio( bktr, AUDIO_MUTE );
if ( set_audio( bktr, *(int*)arg ) < 0 )
set_audio( bktr, AUDIO_EXTERN );
set_audio( bktr, AUDIO_TUNER );
set_audio( bktr, AUDIO_EXTERN );
set_audio( bktr, AUDIO_EXTERN );
set_audio( bktr, AUDIO_EXTERN );
set_audio( bktr, AUDIO_UNMUTE );