The NSO has performed the Fifth some 92 times outside D.C. — on tours, residencies and one-offs stretching back through the tenures of Christoph Eschenbach, Mstislav Rostropovich, Howard Mitchell and Hans Kindler. It’s so easy to think of orchestras as institutions — each one a local congress of instrumental posts passed down through generations of stewards. In reality, an orchestra is about three buses worth of co-workers.