This is something of a historical recording, capturing the distinctive musical moment when Steve Reich's music began to move out of the lofts of Berkeley and Lower Manhattan and into the cultural mainstream. It was recorded in a pair of concerts in 1970, "Four Organs" at the Guggenheim Museum and "Phase Patterns" at the Berkeley Art Museum. Soon after that the album was released, and reissues have followed periodically. Three years later "Four Organs" would still shock audiences in the citadels of culture, accustomed to safe modernism. If you haven't heard these performances, by all means pick up this 2015 reissue. In "Four Organs" and "Phase Patterns," Reich transferred the overlapping and phase-shifting effects of his late-'60s electronic works to conventional instruments. "Four Organs" demands a lot from a maraca player who has to keep an unchanging beat going for more than 15 minutes, but it's an excellent example of early Reich, inexorably proceeding toward its giant chordal finale. "Phase Patterns" is a close cousin to "Four Organs," lacking the percussion and focusing closely on the shifting effect. These are landmarks of the early minimalist movement, still absorbing and compelling in their own right even leaving aside their powerful influence.