To remain relevant, an art form has to be in dialogue with the here and now. Yet in classical music, the bulk of what is performed is still at least a century old. Contrast that with art museums, which present their holdings as a continuum from ancient times to the present, with nearly every major city boasting a contemporary art center and a host of galleries. ... In the last decade or so, a new breed of conservatory-trained musicians has reinvented crossover in unprecedented ways, fusing classical tradition with hip-hop, indie rock and world music and providing new, exciting audience bridges among these forms at the same time.