Ciro Scotto’s Between Rock and a Hard Place underscores the musical connections shared by heavy metal and some avant-garde classic music. Between Rock and a Hard Place-Unplugged is the acoustic companion piece to its electric, electronic and acoustic counterpart. Dan Senn’s Rivus (1985) is scored for unspecified instrumentation of any three treble instruments in the same key, here celeste, glockenspiel and vibes. John Cage’s Five (1988) is part of a series of works known as the “number” pieces. Written for unspecified instrumentation, the McCormick Percussion Group chose bowed vibraphones.