In C

Process music is a movement in which a composition is generated by a clearly defined procedure or rule-set. Sometimes this procedure is made audible—so the listener can follow the gradual changes as they unfold—and sometimes the process remains hidden behind the surface of the sound. Typical processes include phasing (two identical patterns drifting out of sync), additive or subtractive procedures (expanding or contracting a pattern by fixed steps), iterative feedback (repeating an operation so the output becomes the next input), permutations, stochastic or probabilistic rules, or instruction-based performance systems. The aesthetic ranges from hypnotic and pulse-driven to fragile and static, but the core idea remains: the music arises from the process.

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.

Classical music is the notated art-music tradition of Europe and its global descendants, characterized by durable forms, carefully codified harmony and counterpoint, and a literate score-based practice. The term “classical” can refer broadly to the entire Western art-music lineage from the Medieval era to today, not just the Classical period (c. 1750s–1820s). It privileges long-form structures (such as symphonies, sonatas, concertos, masses, and operas), functional or modal harmony, thematic development, and timbral nuance across ensembles ranging from solo instruments to full orchestras and choirs. Across centuries, the style evolved from chant and modal polyphony to tonal harmony, and later to post-tonal idioms, while maintaining a shared emphasis on written notation, performance practice, and craft.