120 Pieces of Sound

Indeterminacy is a strand of post‑war experimental music in which some aspects of a composition are left to chance or to the free choice of the performer, ensuring that no two realizations are exactly the same. The approach encompasses chance procedures used during composition (e.g., tossing coins or consulting the I Ching), open or mobile forms in which sections may be reordered, graphic or text‑based notation that prompts interpretation rather than strict reading, and time‑bracket techniques that specify durations but not exact synchrony. Closely associated with the New York School (John Cage, Earle Brown, Morton Feldman, Christian Wolff), indeterminacy challenged traditional authorship, fixed works, and score‑bound precision by shifting agency to processes and performers. While often conflated with “aleatoric” music, indeterminacy typically denotes unpredictability at the level of performance/realization (open form, variable notation), whereas chance composition may use randomness to create a fixed score. In practice, many works combine both.