Additive process

An additive process is a compositional technique that expands a musical pattern by gradually adding notes or beats, often creating a sense of growth or accumulation.

Ostinato: A short musical pattern repeated persistently, often as a foundation for other material. A recurring pattern gives additions a stable point of reference.
In C: A 1964 composition by Terry Riley built from 53 short musical modules performed in flexible sequence. Its performers repeat and gradually move through patterns, making accumulation central to the work’s form.
Terry Riley: An American composer associated with early minimalist music and improvisational, repetitive forms. His work In C made gradual pattern development central to a landmark ensemble composition.
Additive rhythm: A rhythm formed by combining unequal groups of beats or by progressively lengthening a pattern. It is the clearest rhythmic application of additive construction.
Rhythmic cell: A brief, recognizable arrangement of durations and accents that can be repeated or transformed. Additions often develop a compact rhythmic unit into a longer phrase.
Music for 18 Musicians: A 1976–1978 ensemble work by Steve Reich organized around a sequence of pulsing chords and repeating patterns. Its sections build and transform patterns through gradual changes in their constituent notes.
Steve Reich: An American composer whose music often uses repetition, pulse, and gradual change. His early works explored how patterns can transform through small, audible steps.
Asymmetrical meter: A meter whose beat groups are unequal, such as groups of two and three combined. Adding beats can create or gradually approach an asymmetrical metric cycle.
Metric cycle: A recurring sequence of beats that establishes a musical meter or rhythmic framework. Adding beats can lengthen the cycle before it returns to its starting point.
Clapping Music: A 1972 work by Steve Reich in which two performers repeat the same clapping pattern while one shifts its starting point. Its audible transformation offers a clear contrast between adding material and shifting a pattern.

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Einstein on the BeachBroader topic: Glass uses additive patterns to make small changes audible across extended passages.