Steve Reich composed Phase Patterns in 1970, having just completed another work for organ quartet, Four Organs. The piece draws on Reich's signature phasing technique (multiple layers of the same repeated figure, the layers slipping in and out of sync with each other), as well as his own training as a percussionist, and his awareness of his limitations as a keyboardist. The main rhythmic gesture of the piece is the "paradiddle," a figure borrowed from rudimental drumming consisting of single strokes on each hand followed by a double stroke in one hand (thus, R-L-R-R-L-R-L-L, etc.). Each of the organists plays five- or six-note chords, divided between the hands and executed in paradiddle fashion. The harmonies of the piece remain constant and in fact, the positions of the players' hands on the keyboard likewise remain unchanged, the only variable being the alignment of the paradiddle figures between the four performers. As the downbeats on which the various players' paradiddle figures shift, the overall harmony is filtered through a continually changing surface texture. "I now look at all keyboard instruments," Reich wrote later in a note on Phase Patterns, "as extraordinary sets of tuned drums." In fact, the same paradiddle figuration is used later, with dramatic results, to represent locomotives in the 1988 work for tape and string quartet, Different Trains. ~ Jeremy Grimshaw, All Music Guide
