Phasing can be described simply as playing two identical phrases with a slight metronome difference (one slightly faster than the other). As a result, the two phrases initially sound in unison. Then, when the difference is still very small, a strange perception occurs, as if the notes were stretched out or had a reverb. Later the difference becomes clearly perceptible: the melody also splits in number of notes (2 notes in the time of one). Finally the melody returns in phase, but while one pianist plays the first note, the other plays the second: we thus have bichords instead of the initial unison.
In this piece the process continues through various stages of phase and antiphase, until the two pianists are out of phase to the point where the first note of one overlaps with the last of the other. Thus a small phrase of 12 notes generates a piece of about 20 minutes.
On the October 2006, Peter Aidu (one of the most highly acclaimed modern pianist in Russia) performed the legendary Steve Reich’s composition Piano Phase with an absolutely unique technique. While playing on two pianos, with a left hand on one instrument and the right hand playing separately on the second piano, Peter was recreating the sounding of two performers! This tremendous performance was accurately recorded, and now is available exclusively from Internet Archive.
More in this Internet Archive page.

Steve Reich – Piano phase (1967) – Peter Aidu, 2 pianos
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