Phase music

In 1965, influenced by Terry Riley's use of tape looping and delay, the American composer Steve Reich started experimenting with looping techniques and accidentally discovered the potential of gradual phase shifting as a compositional resource. In discussing the technicalities of what has been termed a "phase shifting process" Reich has stated that it is related to infinite canon or rounds in medieval music. The difference between phase music and traditional rounds, where two or more identical melodies are played with one starting after the other, is that the melodic phrases are generally short repeating patterns with the imitation being variable instead of fixed. ==Electroacoustic phase music==

One early example of electroacoustic phase music is Earle Brown's Music for the Stadler Gallery (1964). The work featured four recordings of the same instrumental piece replayed continuously using four separate tape recorders. Over time, the recordings became increasingly out of phase with one another; the reported total duration of the work being 30 days. This phase based technique was also exploited by Steve Reich in tape works composed between 1965 and 1966. Tape loops of phase-identical segments of recorded sound were played synchronously using multiple tape recorders and were then gradually moved out of phase by increasing or decreasing the playback speed of one of the players. The result of the recordings moving in and out of phase with each other was a transformative process where different timbres, beats, and harmonics were heard; some of which sounded markedly different from the original segment of recorded material. If the sound source had a natural cadence, the phasing created continuously shifting changes to the perceived rhythm as the material drifted in and out of phase. By using additional tracks and loops with identical source material the possibilities for creating a wider range of phasing relationships increases. ==Instrumental phase music==

From 1967 Reich began exploring the gradual phase shifting technique in the context of composed music for instruments. The first of a series of works that would elaborate on this method was Piano Phase, composed in 1967. ==See also==