Minimal music is a form of art music that employs limited or minimal musical materials. In the Western art music tradition the American composers La Monte Young, Terry Riley, Steve Reich, and Philip Glass are credited with being among the first to develop compositional techniques that exploit a minimal approach. It originated in the New York Downtown scene of the 1960s and was initially viewed as a form of experimental music called the New York Hypnotic School. As an aesthetic, it is marked by a non-narrative, non-teleological, and non-representational conception of a work in progress, and represents a new approach to the activity of listening to music by focusing on the internal processes of the music, which lack goals or motion toward those goals. Prominent features of the technique include consonant harmony, steady pulse (if not immobile drones), stasis or gradual transformation, and often reiteration of musical phrases or smaller units such as figures, motifs, and cells. It may include features such as additive process and phase shifting. Phase shifting leads to what has been termed phase music. Minimal compositions that rely heavily on process techniques that follow strict rules are usually described as process music.
The movement originally involved dozens of composers, although only five (Young, Riley, Reich, Glass, and later John Adams) emerged to become publicly associated with American minimal music. In Europe, the music of Louis Andriessen, Karel Goeyvaerts, Michael Nyman, Howard Skempton, Gavin Bryars, Steve Martland, Henryk Górecki, Arvo Pärt and John Tavener exhibits minimalist traits.
It is unclear where the term minimal music originates. Steve Reich has suggested that it is attributable to Michael Nyman, an assertion that two scholars, Jonathan Bernard and Dan Warburton, have also made in writing. Philip Glass believes Tom Johnson coined the phrase.
The word "minimal" was perhaps first used in relation to music in 1968 by Michael Nyman, who "deduced a recipe for the successful 'minimal-music' happening from the entertainment presented by Charlotte Moorman and Nam June Paik at the ICA", which included a performance of Springen by Henning Christiansen and a number of unidentified performance-art pieces. Nyman later expanded his definition of minimal music in his 1974 book Experimental Music: Cage and Beyond. Tom Johnson, one of the few composers to self-identify as minimalist, also claims to have been first to use the word as new music critic for The Village Voice. He describes "minimalism":
The idea of minimalism is much larger than many people realize. It includes, by definition, any music that works with limited or minimal materials: pieces that use only a few notes, pieces that use only a few words of text, or pieces written for very limited instruments, such as antique cymbals, bicycle wheels, or whiskey glasses. It includes pieces that sustain one basic electronic rumble for a long time. It includes pieces made exclusively from recordings of rivers and streams. It includes pieces that move in endless circles. It includes pieces that set up an unmoving wall of saxophone sound. It includes pieces that take a very long time to move gradually from one kind of music to another kind. It includes pieces that permit all possible pitches, as long as they fall between C and D. It includes pieces that slow the tempo down to two or three notes per minute.
Already in 1965 the art historian Barbara Rose had named La Monte Young's Dream Music, Morton Feldman's characteristically soft dynamics, and various unnamed composers "all, to a greater or lesser degree, indebted to John Cage" as examples of "minimal art", but did not specifically use the expression "minimal music".
The most prominent minimalist composers are John Adams, Louis Andriessen, Philip Glass, Steve Reich, Terry Riley, and La Monte Young. Others who have been associated with this compositional approach include Michael Nyman, Howard Skempton, John White, Dave Smith and Michael Parsons. Among African-American composers, the minimalist aesthetic was embraced by figures such as jazz musician John Lewis and multidisciplinary artist Julius Eastman.
The early compositions of Glass and Reich are somewhat austere, with little embellishment on the principal theme. These are works for small instrumental ensembles, of which the composers were often members. In Glass's case, these ensembles comprise organs, winds—particularly saxophones—and vocalists, while Reich's works have more emphasis on mallet and percussion instruments. Most of Adams's works are written for more traditional classical instrumentation, including full orchestra, string quartet, and solo piano.
The music of Reich and Glass drew early sponsorship from art galleries and museums, presented in conjunction with visual-art minimalists like Robert Morris (in Glass's case), and Richard Serra, Bruce Nauman, and the filmmaker Michael Snow (as performers, in Reich's case).
The music of Moondog of the 1940s and 1950s, which was based on counterpoint developing statically over steady pulses in often unusual time signatures influenced both Philip Glass and Steve Reich. Glass has written that he and Reich took Moondog's work "very seriously and understood and appreciated it much more than what we were exposed to at Juilliard".
One of the first minimalist compositions was November by Dennis Johnson, written in 1959. A work for solo piano that lasted around six hours, it demonstrated many features that would come to be associated with minimalism, such as diatonic tonality, phrase repetition, additive process, and duration. La Monte Young credits this piece as the inspiration for his own magnum opus, The Well-Tuned Piano.
In 1960, Terry Riley wrote a string quartet in pure, uninflected C major.[clarification needed] In 1963, Riley made two electronic works using tape delay, Mescalin Mix and The Gift, which injected the idea of repetition into minimalism. In 1964, Riley's In C made persuasively engaging textures from layered performance of repeated melodic phrases. The work is scored for any group of instruments and/or voices. In 1965 and 1966 Steve Reich produced three works--It's Gonna Rain and Come Out for tape, and Piano Phase for live performers--that introduced the idea of phase shifting, or allowing two identical phrases or sound samples played at slightly differing speeds to repeat and slowly go out of phase with each other. Starting in 1968 with 1 + 1, Philip Glass wrote a series of works that incorporated additive process (form based on sequences such as 1, 1 2, 1 2 3, 1 2 3 4) into the repertoire of minimalist techniques; these works included Two Pages, Music in Fifths, Music in Contrary Motion, and others. Glass was influenced by Ravi Shankar and Indian music from the time he was assigned a film score transcription of music by Ravi Shankar into western notation. He realized that in the West time is divided like a slice of bread; Indian and other cultures take small units and string them together. 
According to Richard E. Rodda, "'Minimalist' music is based upon the repetition of slowly changing common chords [chords that are diatonic to more than one key, or else triads, either just major, or major and minor--see: common tone] in steady rhythms, often overlaid with a lyrical melody in long, arching phrases...[It] utilizes repetitive melodic patterns, consonant harmonies, motoric rhythms, and a deliberate striving for aural beauty." Timothy Johnson holds that, as a style, minimal music is primarily continuous in form, without disjunct sections. A direct consequence of this is an uninterrupted texture made up from interlocking rhythmic patterns and pulses. It is in addition marked by the use of bright timbres and an energetic manner. Its harmonic sonorities are distinctively simple, usually diatonic, often consist of familiar triads and seventh chords, and are presented in a slow harmonic rhythm. Johnson disagrees with Rodda, however, in finding that minimal music's most distinctive feature is the complete absence of extended melodic lines. Instead, there are only brief melodic segments, thrusting the organization, combination, and individual characteristics of short, repetitive rhythmic patterns into the foreground.
Leonard Meyer described minimal music in 1994:
Because there is little sense of goal-directed motion, [minimal] music does not seem to move from one place to another. Within any musical segment there may be some sense of direction, but frequently the segments fail to lead to or imply one another. They simply follow one another.
David Cope (1997) lists the following qualities as possible characteristics of minimal music:
Robert Fink (2005), offers a summary of some notable critical reactions to minimal music:
[...] perhaps it can be understood as a kind of social pathology, as an aural sign that American audiences are primitive and uneducated (Pierre Boulez); that kids nowadays just want to get stoned (Donal Henahan and Harold Schonberg in the New York Times); that traditional Western cultural values have eroded in the liberal wake of the 1960s (Samuel Lipman); that minimalist repetition is dangerously seductive propaganda, akin to Hitler's speeches and advertising (Elliott Carter); even that the commodity-fetishism of modern capitalism has fatally trapped the autonomous self in minimalist narcissism (Christopher Lasch).
Elliott Carter maintained a consistent critical stance against minimalism and in 1982 he went so far as to compare it to fascism in stating that "one also hears constant repetition in the speeches of Hitler and in advertising. It has its dangerous aspects." When asked in 2001 how he felt about minimal music he replied that "we are surrounded by a world of minimalism. All that junk mail I get every single day repeats; when I look at television I see the same advertisement, and I try to follow the movie that's being shown, but I'm being told about cat food every five minutes. That is minimalism." Fink notes that Carter's general loathing of the music is representative of a form of musical snobbery that dismisses repetition more generally. Carter has even criticised the use of repetition in the music of Edgard Varèse and Charles Ives, stating that "I cannot understand the popularity of that kind of music, which is based on repetition. In a civilized society things don't need to be said more than three times."
Ian MacDonald claimed that minimalism is the "passionless, sexless and emotionally blank soundtrack of the Machine Age, its utopian selfishness no more than an expression of human passivity in the face of mass-production and The Bomb".
Steve Reich has offered one possible explanation for why such criticism is largely misplaced. In 1987 he stated that his compositional output reflected the popular culture of postwar American consumer society because the "elite European-style serial music" was simply not representative of his cultural experience. Reich stated that
Stockhausen, Berio, and Boulez were portraying in very honest terms what it was like to pick up the pieces after World War II. But for some American in 1948 or 1958 or 1968--in the real context of tailfins, Chuck Berry and millions of burgers sold--to pretend that instead we're really going to have the darkbrown Angst of Vienna is a lie, a musical lie.
Kyle Gann, himself a minimalist composer, has argued that minimalism represented a predictable return to simplicity after the development of an earlier style had run its course to an extreme and unsurpassable complexity. Parallels include the advent of the simple Baroque continuo style following elaborate Renaissance polyphony and the simple early classical symphony following Bach's monumental advances in Baroque counterpoint. In addition, critics have often overstated the simplicity of even early minimalism. Michael Nyman has pointed out that much of the charm of Steve Reich's early music had to do with perceptual phenomena that were not actually played, but resulted from subtleties in the phase-shifting process. In other words, the music often does not sound as simple as it looks.
In Gann's further analysis, during the 1980s minimalism evolved into less strict, more complex styles such as postminimalism and totalism, breaking out of the strongly framed repetition and stasis of early minimalism, and enriching it with a confluence of other rhythmic and structural influences.
Minimal music has had some influence on developments in popular music. The experimental rock act The Velvet Underground had a connection with the New York down-town scene from which minimal music emerged, rooted in the close working relationship of John Cale and La Monte Young, the latter influencing Cale's work with the band. Terry Riley's album A Rainbow in Curved Air (1969) was released during the era of psychedelia and flower power, becoming the first minimalist work to have crossover success, appealing to rock and jazz audiences. Music theorist Daniel Harrison coined the Beach Boys' Smiley Smile (1967) an experimental work of "protominimal rock", elaborating: "[The album] can almost be considered a work of art music in the Western classical tradition, and its innovations in the musical language of rock can be compared to those that introduced atonal and other nontraditional techniques into that classical tradition." The development of specific experimental rock genres such as krautrock, space rock (from the 1980s), noise rock, and post-rock was influenced by minimal music.
Sherburne (2006) has suggested that noted similarities between minimal forms of electronic dance music and American minimal music could easily be accidental. Much of the music technology used in dance music has traditionally been designed to suit loop-based compositional methods, which may explain why certain stylistic features of styles such as minimal techno sound similar to minimal art music. One group who clearly did have an awareness of the American minimal tradition is the British Ambient act The Orb. Their 1990 production "Little Fluffy Clouds" features a sample from Steve Reich's work Electric Counterpoint (1987). Further acknowledgement of Steve Reich's possible influence on electronic dance music came with the release in 1999 of the Reich Remixed tribute album which featured reinterpretations by artists such as DJ Spooky, Mantronik, Ken Ishii, and Coldcut, among others.