Piano Phase

Piano Phase is minimalist composition by American composer Steve Reich, written in 1967 for two pianos (or piano and tape). It is one of his first attempts at applying his "phasing" technique, which he had previously used in the tape pieces It's Gonna Rain (1965) and Come Out (1966), to live performance.

Reich further developed this technique in pieces like Violin Phase (also 1967), Phase Patterns (1970), and Drumming (1971).

Piano Phase represents Steve Reich's first attempt to apply his "phasing" technique. Reich had earlier used tape loops in It's Gonna Rain (1965) and Come Out (1966), but wanted to apply the technique to live performance. Reich carried out a hybrid test with Reed Phase (1966), combining an instrument (a soprano saxophone) and a magnetic tape.

Not having two pianos at his disposal, Reich experimented by first recording a piano part on tape, and then trying to play mostly in sync with the recording, albeit with slight shifts, or phases, with occasional re-alignments of the twelve successive notes against each other. Reich found the experience satisfying, showing that a musician can phase with concentration.

With the premiere of Reed Phase at Fairleigh Dickinson University in early 1967, Reich and a musician friend, Arthur Murphy, had the opportunity to attempt Piano Phase with two pianos in live concert. Reich discovered that it was possible to dispense with tape and phase without mechanical assistance. Reich experimented phasing with several versions, including a version for four electric pianos titled Four Pianos dating from March 1967, before settling on a final version of the piece written for two pianos. The creation of the version for four pianos was conducted March 17, 1967 at the Park Place Gallery, with Art Murphy, James Tenney, Philip Corner, and Reich himself.

...
Wikipedia