What does "pattern games" signify, in the context of Steve Reich's Music for 18 Musicians?

Question

Source: The Complete Classical Music Guide (2012). General Editor: John Burrows OBE HonRCM, edited with Charles Wiffen. p. 297 Bottom Left.

MUSIC FOR 18 MUSICIANS [...]

This big, single-movement piece, created in 1974 and 1975 for an enlarged form of Reich’s own ensemble, has a good claim to be his masterpiece. What makes it so irresistible is the way the moment-to-moment unfolding of Reich’s familiar “pattern games” is embedded in a convincing architectural frame. The division of the ensemble into “breathing” wind instruments and voice and “pulsing” instruments gives rise to a layered texture, with slow-moving phrases set against pattering activity.

What does the emboldened noun mean?

Answer 1

Steve Reich has always had an interest in composing music from patterns or processes, and a technique he refers to as phasing (see below).

Early statement (1987) Music as a gradual process.

"Though I may have the pleasure of discovering musical processes and composing the musical material to run through them, once the process is set up and loaded it runs by itself."

This review of Reich's 'Writings about Music' touches on this also :

"... a new relationship between material and form; not merely the repetition of musical patterns, but the psychology of listening to such repetition; not merely processes of gradual change, but music in which progressive transformation has become the syntax of the language."

Assmbling a piece from a set of repeated patterns is common with him, for example Drumming. The notes on the YT entry for this piece also touch on this : "The piece employs Reich's trademark technique of phasing. Phasing is achieved when two players, or one player and a recording, are playing a single repeated pattern in unison, usually on the same kind of instrument. One player changes tempo slightly, while the other remains constant, and eventually the two players are one or several beats out of sync with each other. They may either stay there, or phase further, depending on the piece."

On the way that this applies to "Music for 18 musicians" : Composer's notes to Boosey and Hawkes edition.

"The structure of Music for 18 Musicians is based on a cycle of eleven chords played at the very beginning of the piece and repeated at the end. All the instruments and voices play or sing the pulsating notes with each chord. Instruments like the strings which to not have to breath nevertheless follow the rise and fall of the breath by following the breathing patterns of the bass clarinet. Each chord is held for the duration of two breaths, and the next chord is gradually introduced, and so on, until all eleven are played and the ensemble returns to the first chord"