In the closing days of the Philharmonic's inaugural celebration of new music, Mr. Pintscher leads the New York premieres of his own "Reflections on Narcissus" (2004-5), with Ms. Weilerstein, a vibrant cellist, and "Instances" (2012), Elliott Carter's final completed work. There will also be a new piece selected through the American Composers Orchestra's EarShot National Orchestral Composition Discovery Network.