phasing

A minimalist technique in which two or more voices play the same or similar material at a slight temporal offset, creating interference patterns, echo effects, and rhythmic complexity from simple source material. Steve Reich's 1967 Piano Phase is the canonical solo piano example. Adams uses phasing in Hallelujah Junction — the two pianos play nearly identical figures with slight delays between them, as if one piano is processing the other through a delay circuit.

In phased passages, resist the instinct to align with your duo partner — the slight displacement is the intended sound. Maintain your own steady pulse without listening for a unison that will never arrive. The listener's perception of pulse will fluctuate between the two players' rhythms, creating a shimmer the two pianos cannot produce alone.