One of Terry Riley's most enduring works, and a haunting record that contains two extended modal minimal jams. By capturing Riley as both a conceptualist and as a virtuoso performer, this 1969 LP revealed a suppleness that stands in contrast to the baggage associated with “minimalism.” The range displayed over its two sides reaches out to the world (and, yes, the cosmos) rather than sitting inside any restrictive aesthetic field. As a result, the album can simultaneously suggest a feel of hurtling liftoff as well as one of peaceable calm. Side A’s heavily overdubbed title track features the composer on a range of keys: electric organ, electric harpsichord, rocksichord (also a favorite of Sun Ra’s), as well as two percussion items (dumbec and tambourine). Once the fast, opening pattern of “Rainbow” has been established, a series of placid chords superimposes a sense of ease. And then comes an explosion, a procession of right-hand lines that flutter and pirouette over the over the pulsing rhythmic patterns. That this powerful influx of energy doesn’t make the music feel cluttered or harsh is one of Riley’s compositional achievements.
"Poppy Nogood & The Phantom Band" has a similar groove on organ and soprano saxophone. The composer’s integration of avant-garde then-revolutionary overdubbing and tape-looping techniques within a jazz-influenced style helps communicate this album’s roving, idealistic feel. The repetitious minimalism of Rainbow also was integral to the development of future genres, such as ambient, jazz fusion, new age, progressive rock, and future varieties of electronic music. More than just a revolutionary record, Rainbow also represented one final burst of sunny, utopian energy, as the dark and dreary 1970s loomed overhead.