The long collaboration of Merce Cunningham (choreography) and John Cage (music) is one of the most significant developments in twentieth-century theatre. John Cage has defined theatre this way:

I try to make definitions that won't exclude. I would simply say that theatre is something which engages both the eye and the ear. The two public senses are seeing and hearing; the senses of taste, touch, and odor are more proper to intimate, non-public situations. The reason I want to make my definition that simple is so one could view everyday life itself as theatre.