This idea of phasing is simple with electronics, as it is fairly straight-forward to calibrate technology to produce a desired result.  However, Reich was at one point convinced this could not exist with acoustic instruments played by humans.  As another experiment, he decided to act as a “second tape recorder” and after recording a pattern that would eventually become Piano Phase he started in unison with the recording and slowly tried to get ahead of it.  The experiment ultimately worked, the outcome being the realization of the ability of humans to phase rhythmically, an initially unnatural instinct for most of us.

Ultimately, phasing takes on a similar life as the most basic canon.  In its most basic form, a canon consists of a musical idea followed by a second version of itself offset by a chosen number of beats.  Likewise, the phasing in Reich’s music, or in any music where this technique is employed, begins with a basic musical idea and is followed with a second version of itself gradually progressing towards a desired product (i.e., a pattern offset by a sixteenth-note, eighth-note, etc.).  The difference lies in the method by which each is achieved:  canon in two-measure phrases is inherent in the composition, and phasing is achieved through changes in tempo gradually over a period of time.

The video below illustrates the concept of phasing both musically and visually.  This choreography set to Reich’s Piano Phase is outstanding and as you watch and listen, you begin to understand the idea of time being a construct.  Within that construct things are set in motion, and given proper life within the construct, will fall in and out of perfect relationships with each other (i.e., phasing).

Some Reading On the Topic

An excellent article by Paul Epstein appeared in The Musical Quarterly in 1986.  Entitled, “Pattern Structure and Process in Steve Reich’s “Piano Phase,” it not only dissects the formal process of creating the phases, but also explains the phenomenon of phasing in terms comprehensible by most with any sort of musical training.  It is available online through JSTOR (you must have access through a university or other scholarly organization), and the citation follows below.

Epstein, Paul.  “Pattern Structure and Process in Steve Reich’s “Piano Phase.”  The Musical Quarterly, Vol. 72, No. 4. (1986): 494-50.

Steve Reich, born in New York in 1936, redefined musical composition in the latter years of the twentieth century. Having studied with such notable composers as Vincent Persichetti, Luciano Berio, and Darius Milhaud, Reich is well-versed in both serial and tonal techniques. This eclectic background led him to consider other elements for composition aside from the usual melody with harmony. While these elements exist in his music, Reich has focused some of his works entirely on rhythm (Clapping Music, 1972), phasing and timbre (Piano Phase, 1967), and specific harmonic and register considerations (Music for 18 Musicians, 1976). According to Reich,

What I’m interested in is a compositional process and a sounding music that are one in the same thing.

His studies in philosophy and music, coupled with studies in African drumming, Gamelan music, and Hebrew cantillation have awarded him countless times. In addition to Reich and his formed ensemble of Musicians selling out Carnegie Hall, he has won two Grammy Awards, been selected to the American Academy of Arts and Letters, the Bavarian Academy of Fine Arts, and awarded membership to the Franz Liszt Academy in Budapest.

Reich’s works have been performed by the world’s top orchestras and ensembles. In Tokyo in 2007, he was awarded the prestigious Preamium Imperial Award in Music, an international award given in areas of the arts not covered by the Nobel Prize.

As for the certain je ne sais quoi, it is a testament to Reich’s ability to seamlessly blend the process, with the music.

Clapping Music, by Steve Reich

Other Notable Works:

Piano Phase (1967), for two pianos

Music for Pieces of Wood (1973), for pitched claves

Different Trains (1988), for string quartet and tape

Three Tales (2001), a three-act digital video opera, recalling three events of the twentieth century: the Hindenburg disaster (1937); Bikini Atoll atomic testing (1946-54); Cloning of Dolly the Sheep (1997)