Steve Reich has described his 1971 piece Four Organs as an attempt to reproduce the phasing effect of his mid-'60s tape pieces (such as Come Out and It's Gonna Rain) with real musicians in a concert setting. Four organists (including on this 1974 recording, both Reich himself and his friend Philip Glass) play single notes repeatedly, aided by the superhuman efforts of a maracas player who's providing an unaccented beat at a steady tempo. As beats are slowly added to and dropped from bars as the piece develops, chords that had formed and lasted for single beats in early measures become longer and longer, so that by the end of the piece, a single chord, formed by the four organists each playing a different note, is held for over 200 beats. As an added textural fillip, human nature requires that, despite their best efforts, the organists will not be hitting every note at exactly the same time, thus producing the interesting textures and overtones that start to become the focus of the piece after the first couple of minutes. Four Organs is minimalism at its purest. Phase Patterns is basically the same idea without the steadying influence of the maracas, meaning that the phasing effects occur quicker and are more pronounced. It's arguably a slightly less interesting work, but it's still one of Reich's finest early pieces.