Composers: Of Dice and Din

John Cage was in his element—chaos. The audience of 7,000 wandered to and fro in the University of Illinois Assembly Hall. Wandering happily right along with them, Cage drank in the beeps, doinks and sputterings coming from loudspeakers spaced along the walls. He gazed serenely at the color-crazy patterns sprayed by rotating slide projectors on the walls and the temporary translucent ceiling. He stared at the NASA space films and the clips from the silent era that flickered on the movie screens.

A student stepped up, handed Cage a book and asked him to autograph it: "In view of what's...