REICH: SEXTET; "SIX MARIMBAS." Steve Reich and Musicians, with members of Nexus; Bob Becker, Russ Hartenberger, marimbas, with members of the Manhattan Marimba Quartet. Nonesuch 79138 (digital). The Sextet is the more intriguing and more exhilarating of these two chamber pieces by this most cerebral of minimalists. Possibly because it was co-commissioned by choreographer Laura Dean, the 1984-85 work spreads its thematic ranger wider and varies its rhythmic underpinnings more theatrically than most of Reich's recent non-vocal output. "Six Marimbas" rescores the 1971 "Six Pianos" to excellent effect, pursuing its obsessive figure-and-ground patterns for a mesmerizing 16 minutes. Highly charged performances, vivid sonics.