We've heard plenty about the Verdi and Wagner bicentennials this year, but there's another noteworthy birthday on the calendar: the centenary of English composer Benjamin Britten. You'll see programs here and there throughout the fall, but none as ambitious as Celebrating Britten, a four-month series presented by Trinity Wall Street. Kicking things off this afternoon, tenor Nicholas Phan and mezzo-soprano Virginia Warnken join conductor Julian Wachner and Novus NY for Britten's Sinfonietta, Nocturne and Phaedra. Then on Sept 8, Wachner leads the Trinity Youth Chorus in The Little Sweep. See trinitywallstreet.org for a complete list of events.