“You are the music/ While the music lasts.” Whatever these words mean in Eliot’s Four Quartets, they have often been given new meaning in dance, and nowhere more so than in the solos choreographed by Merce Cunningham. He is the choreographer whose most radical, controversial, and profound contribution to choreography was to separate it from music — or so it seemed. The dance that the audience saw and the music that it heard were composed independently. The audible music, which often varied unpredictably at each performance, operated separately, sometimes like a hostile environment. What was easy to miss was that, whereas most dance responded to heard music, Cunningham’s dance embodied many unheard musics. It was a theatrical adventure without serious precedent: sometimes the dancers seemed to be at one with “the music of the spheres.”