Commemorating the 20th anniversary of the September 11 attacks, Yannick Nézet-Séguin leads the majestic Met Orchestra and Chorus in what for many music lovers remains—with all due respect to Mozart, Berlioz, Brahms, Duruflé, and Britten—the requiem of requiems, and not just the most operatic. In Ailyn Pérez, Elīna Garanča, Matthew Polenzani, and Eric Owens, he has assembled the kind of all-star quartet the music and the occasion demand. —M.G.