The French word "Passe-partout" means "Master Key". As the title implies, this music serves as a key that unlocks the door to the possibility of an unlimited variety of instrumental combinations. The music in these books is readily playable by any, or all, of the instruments that are depicted inside the ring of the key on the cover of each book. The instruments listed at the side of the key state which can play along by using other books of this series with the same title. The music is composed by Chris Wiggins and is light, entertaining and ideally suitable as lesson material. Above all it is music simply to be enjoyed by both player and listener alike.