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Systems music is a term which has been used to describe the work of composers who concern themselves primarily with sound continua which evolve gradually, often over very long periods of time (Sutherland 1994, 172). Historically, the American minimalists Steve Reich, La Monte Young and Philip Glass are considered the principal proponents of this compositional approach. Works by this group of composers are often characterized by features such as stasis or repetitiveness.
A number of English experimental composers have also developed systems based music particularly Michael Parsons, Howard Skempton, John White, and Michael Nyman (Sutherland 1994, 183). This form of systems music is more commonly referred to as "minimalism".
In the realm of computer music, "systems music" refers to fractal-based, computer-assisted composition, and in particular iterated function systems music, in which a function "is applied repeatedly, each time taking as argument its value at the previous application" (Gogins 1991, 40).
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'Machine processes', developed by John White evidenced a systems approach. Machine processes typically had a repetitive structure generated by random processes (dart boards, random number tables, chess moves). A typical 'Machine piece' of this genre is White's Drinking and Hooting Machine (1968), in which each player performs by blowing over the top of a bottle of 'a favoured drink', then altering the tone of the bottle by taking sips, swigs, or gulps from the drink (or leaving it alone) from a table of numbers obtained through random processes.
A form of systems is the 'found system', preferred by Christopher Hobbs, in his work Aran (1971), in which a knitting pattern for an Aran sweater, with its different stitches, determines the pitches chosen and the instruments to play them, and in his recent series of pieces called Sudoku Music (2005-6), using 'super' or 'mega' sudoku puzzles having a hexadecimal (16 x 16) grid.
The Hobbs-White Duo performed what could be called 'classic' or strict systems, particularly in their percussion music, in which various permutations of durations or of instruments were observed rigorously. Michael Parsons and Howard Skempton also performed as a systemic percussion duo. Parsons' systems for piano often focused on alternations and permutations of distinct intervals. The piano duo of Dave Smith and John Lewis also worked in some systems in the 1970s, Lewis in terms of reggae and other popular music influences. Smith has used permutations in his titles, often of funny anagrams, but he has occasionally used systemic processes.
Michael Nyman also worked with repetitive systems. In his earliest work he often used structures either borrowed from or influenced by West Coast and other minimalism only with a particularly English sensibility in his choice of musical material. Waltz in F, for instance, uses a structure akin to Terry Riley's In C, but the musical material is that of almost-clichéd waltz figurations. It was Nyman's work as a critic as well as his status as one of the best-known British experimental composers that the term 'systems' became used in the 1980s as a generic term for all minimalism. Since then it has erroneously been considered to be an archaic term for minimalism, even though systemic composition is still ongoing in Britain.
In the 1980s, much of the numerical systems work was applied in early computer music (as in White's series of electronic symphonies) or for early electronic and MIDI keyboards (Hobbs' Back Seat Album has one movement in which the completion of a permutation is celebrated by a rising electronic figuration). Although most British experimentalists use other types of generation – mostly eclectic, through-composed, often tonal work using surprising juxtapositions of references and of modulation – many use larger-form systems occasionally, if they no longer use the strict note-to-note systems. Hobbs' Fifty in Two-Thousand (2000) is typical, in that large blocks of distinct melodic sections with varying instrumentation are arranged and repeated according to a permutational structure.
- Gogins, Michael (1991). "Iterated-Functions Systems Music". Computer Music Journal 15, no. 1 (Spring): 40–48.
- Sutherland, Roger (1994). New Perspectives in Music. London: Sun Tavern Fields. ISBN 0-9517012-6-6.
- Dennis, Brian (1974). "Repetitive and Systemic Music". The Musical Times 115, no. 1582 (December), pp. 1036–38.