The Philadelphia Orchestra just hired a new music director, writes Peter Dobrin. But it’s not too soon to be looking for his successor. “All the major orchestras have experienced change at the helm in the last decade; orchestras everywhere seem to be in a perpetual state of search. Chicago is looking for a new music director, and no sooner will it announce a choice than New York will reveal that it is in the market. Such is the pace of a peripatetic profession. Ideally, Philadelphia would be developing relationships with conductors now, so that when it finds itself looking for new leadership, an actual leader will already be in the pipeline.”