Composed: 1979

Length: 25 minutes

Orchestration: 3 flutes, 3 oboes, 3 trumpets, 3 trombones, tuba, 3 electric organs, 2 pianos, and strings

First Los Angeles Philharmonic performances

Composing for an ensemble other than his own marked a radical departure for Reich; not surprisingly, its musical results were also radical: "The constant yet slow harmonic change (there are no repeat markings in this score), the slow recurrence of materials from variation to variation, and the scoring for oboes, flutes, full brass, strings, acoustic and electric keyboards, all give this piece a sound quite different from my earlier music."

The title tells us what instrumental forces these variations are for. But what are they on? Normally, a set of variations departs from a theme; the composer tries to make the theme memorable enough in both structure and tune that the listener can appreciate the variations. Not so here: in spite of a catchy motive that undergoes variation, the title actually refers to a long harmonic progression whose three statements define variations of approximately six, ten, and nine minutes.

Reich notes that the distribution of parts is integral to his design: "The harmonic progression is followed in the middle register so that from time to time the bass may vary from variation to variation. The rhythm of the melodic patterns in the winds remains more or less constant throughout each variation, while the notes slowly, yet constantly, change to match the changing harmony… At all times throughout the piece there are at least two wind instruments playing the melodic pattern in harmony with each other, while a third plays in canon with the upper voice. The winds, three oboes doubled by electric organs, or three flutes doubled by two pianos and electric organs, play the melodic material throughout, while the slowly changing harmonies are played by the strings also doubled by electric organs. During the first and last variation a full brass section of three trumpets, three trombones, and tuba gradually fade in and out, to complete the harmony of the middle register strings and organs."

Reich's uses of variable meters keeps the ear engaged; as the piece progresses, a gradual increase in smaller note values gives, in his words: "the effect…of becoming more florid and melismatic." Throughout, the play of surface and depth is particularly imaginative. A listener can certainly hear points of harmonic arrival, but because the progression is so long, it is difficult to assess their structural hierarchy. Thus the conventional listening experience - in which the structural outlines are clear so that the surface variations emerge clearly - is turned upside-down, and the listener has no choice but to stay in the moment.

- Susan Key is a musicologist and frequent contributor to Los Angeles Philharmonic programs, specializing in American music.