The piece begins with three pianists playing different notes to the same 8-beat rhythmic pattern. Then two more pianists begin to play the same pattern shifted two beats out of phase. (Phasing is a prominent technique in most of Steve Reich's work.) Different phase shifts of the same motifs fade in and out of the ever-changing musical texture for the duration of the piece. Six Pianos is also notable by being one of Reich's only pieces in duple time.
Six Pianos has three sections, separated by relatively sudden changes of tonal center, though they all use the same seven pitch classes of the D major diatonic scale. The first section is in D major, with the tonality anchored in place by a persistent pattern of D and A in the bass. Then that pattern slowly fades out, leaving a B minor tonality which serves as a short transition to the second section in E Dorian. A sudden transition leads to the third section in B natural minor. Six Marimbas follows the same structure, but is transposed down by one semitone so that the piece opens in D flat major and concludes in B flat natural minor.