playMusic(clip0, clip1)
From pinHeck Wiki
Example:
playMusic('M', 'N');
Plays the file #MN.wav from the SFX/_FZ folder. Music files loop by default unless you set otherwise. For best results, create long looping versions of the music in the file (5-8 minutes per file) so you can make nice looping transitions. The system's loop ends the file and restarts it again, which will not result in as clean of a transition.
Music files must be in the SFX/_FZ folder and have a 3 character filename always starting with '#'
Example: #AB.wav