David Robertson conducts the New York Philharmonic. So? There is a sense that younger conductors are being given chances to work with the orchestra with an eye to the future. “To the credit of the current music director, Lorin Maazel, the orchestra has done a much better job of introducing promising younger conductors — and potential successors — to its podium, musicians like Robert Spano and Alan Gilbert, as well as Osmo Vanska and Gianandrea Noseda, who made their debuts recently.”