At first it was hard to tell if it had begun, and what exactly it was. So Percussion had quietly positioned themselves in one corner of the stage and the lights had dimmed, and when the Museum of Fine Art's sold-out Remis Auditorium had hushed itself we began to hear a net of beads rubbing around a gourd-shaped object in front of a microphone. This gentle clacking was joined by some barely-perceptible fuzz and......