In playing his motives, the instrumentalists in Riley’s In C interact with each other in ways largely unspecified by the composer. One might linger over a particular motive, repeating it while another moves on to other motives. In C thus exemplifies the chance music we mentioned earlier. This term covers a great variety of music in which certain elements specified by the composer in more conventional music are left to chance. Another element of In C that is left up to the performer is its instrumentation — who plays what. Riley says only that it can be played by “any number of any kind of instruments.”

In an extreme case, a chance composer might work out a way of throwing dice so as to determine which instruments, which pitches, and so on were to be used. In a less extreme case, a performer getting to a certain place in a piece would be told to play anything at all, so long as it was (for example) loud and fast. Strictly speaking, what would be heard would be determined by chance, but the composer could count on a type of controlled chaos for a limited span of time, a span situated between two passages of fully written-out music.

Whereas earlier modernists had questioned traditional assumptions about melody, dissonance, and meter, chance composers questioned even more basic assumptions about musical time. The musical forms we have studied throughout this book tend to mark off time as a clear linear progress and even make it goal-directed: Think of the move from development to recapitulation in a Beethoven sonata form. Is time always (chance composers would ask: is it ever) actually experienced in this way? Even In C is felt to be goal-directed in a certain sense, for as the snippets in the margin on page 362 show, the pitches get a little higher and the rhythmic activity intensifies as the piece proceeds.

But must music convey such an experience? Could it instead mark time as a random sequence of events, or even as timeless, like the suspended consciousness we experience in certain kinds of meditation? Such questions, and a passive sense of time that cuts against our goal-directed culture, lie at the root of chance music.