Great Noise Ensemble struggles to get its balances right

Mozart is said to have remarked that "music means only itself." If ever there was a piece that epitomizes this, it's Steve Reich's "Music for 18 Musicians," an hour of slowly evolving layers of timbres, harmonies and rhythms anchored by an unrelenting beat. Scored for a violin, cello, a couple of clarinets, four female voices, maracas, four pianos and a stage full of marimbas, xylophones and a vibraphone, it can be mesmerizing or, as it was for the gentleman across the aisle from me, merely back...