al_attach_mixer_to_mixer - Allegro 5 API

       Attaches  the mixer passed as the first argument onto the mixer passed as the second argument.  The first
       mixer (that is going to be attached) must not already be attached to anything.  Both mixers must use  the
       same frequency, audio depth and channel configuration.

       Returns true on success, false on error.

       It is invalid to attach a mixer to itself.

       al_attach_mixer_to_mixer - Allegro 5 API

al_detach_mixer(3alleg5).

Allegro reference manual                                                       al_attach_mixer_to_mixer(3alleg5)

              #include <allegro5/allegro_audio.h>

              bool al_attach_mixer_to_mixer(ALLEGRO_MIXER *stream, ALLEGRO_MIXER *mixer)