al_set_audio_stream_pan - Allegro 5 API
bool al_set_audio_stream_pan(ALLEGRO_AUDIO_STREAM *stream, float val)
Set the pan value on an audio stream. A value of -1.0 means to play the stream
only through the left speaker; +1.0 means only through the right speaker; 0.0
means the sample is centre balanced. A special value
ALLEGRO_AUDIO_PAN_NONE(3alleg5) disables panning and plays the stream at its
original level. This will be louder than a pan value of 0.0.
Returns true on success, false on failure. Will fail if the audio
stream is attached directly to a voice.