Process music is a form of experimental and minimalist composition in which a clear, rule-based procedure generates the musical material and its transformation over time.
Rather than traditional themes and development, the listener perceives the unfolding of a system—such as phasing, gradual addition or subtraction, substitution, stochastic change, or feedback—as the primary musical idea.
The materials are often limited (short cells, drones, or simple harmonies), the pace of change is typically gradual, and the structure is transparent so that the process itself becomes the aesthetic focus.
Although associated with American minimalism, process music also includes works driven by mathematical or physical procedures, tape-loop iterations, and acoustic phenomena that reveal the process audibly.
Process music cohered in the United States during the 1960s, when composers began foregrounding the audible working-out of a musical procedure as the artwork itself. Terry Riley’s In C (1964) introduced a cellular, additive approach with performer-driven repetition and alignment. Steve Reich’s tape-loop phasing pieces It’s Gonna Rain (1965) and Come Out (1966), followed by live phasing in Piano Phase (1967), made gradual, rule-governed shift the central subject. La Monte Young’s sustained-tone works and tuning systems framed long-duration, slowly changing processes, while Philip Glass developed additive processes that accumulate or subtract notes against a steady pulse. In his 1968 essay “Music as a Gradual Process,” Reich explicitly articulated the aesthetic: the process should be perceptible to the listener.
Related tendencies were already present in experimental and avant-garde circles. John Cage’s indeterminacy and chance operations, serial and post-serial procedures, and electroacoustic/tape techniques (including musique concrète) provided toolkits for rule-based composition. Iannis Xenakis’s stochastic methods (e.g., Pithoprakta, 1950s) and James Tenney’s psychoacoustic processes pointed to mathematically and perceptually driven systems. These strands converged as composers pursued pieces where the listener could follow the system at work.
The 1970s saw process approaches diversify: Alvin Lucier explored acoustic feedback and room resonance (I am sitting in a room, 1970); Tom Johnson wrote rigorously rule-based, text-explained pieces; Frederic Rzewski used textual/motivic processes (Coming Together, 1971); and Cornelius Cardew’s experimental scores engaged open, procedural performance practices. Process thinking fed directly into post-minimalism and shaped developments in sound art, installation, and long-duration concert forms. As digital tools matured, algorithmic, generative, and iterative workflows made process methods both practical and central across experimental and popular contexts.
With computers, live electronics, and software environments, composers codified processes as algorithms, enabling real-time generative music, live coding, and interactive installations. Process music’s emphasis on transparency and gradualism informed ambient, minimal techno, and trance structures, while its systems mindset influenced contemporary electroacoustic composition, multimedia art, and data-driven works. Today, the term encompasses both acoustic and electronic practices so long as the perceivable unfolding of a rule-based procedure remains the musical focus.
Select a simple, rule-based procedure whose unfolding can be heard: phasing two identical loops at slightly different speeds; additive or subtractive growth of a cell; systematic substitution of notes; stochastic changes governed by a probability table; or acoustic feedback that transforms a signal iteratively.
Use a small pitch set (e.g., a mode, pentatonic, or a few dyads), a short rhythmic cell, or a sustained drone. The restraint makes the process audible and the changes meaningful.
Decide on a steady pulse (common in minimalist process pieces) or a beatless frame (as in feedback or resonance processes). Let changes occur gradually so listeners can track them. Avoid adding unrelated gestures that distract from the rule.
Design the piece as the duration of the process itself (e.g., until sync realigns, until saturation, or for a fixed time). Use text scores or concise traditional notation that states the rule and starting materials. Provide click tracks or cues if tight alignment is required; allow performer latitude when variability is part of the process.
Rehearse at multiple tempi and lengths. If the transformation is imperceptible, increase the rate slightly; if it feels abrupt, slow it down or simplify parameters. Keep the focus on hearing the system, not on virtuoso embellishment.
