Piano Phase is a 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).