Polyphony and Stephen Layton present highlights from the choral repertoire by four twentieth-century American giants: Samuel Barber, Leonard Bernstein, Aaron Copland and Randall Thompson. Framed by Thompson's understated favorites Alleluia and Fare Well, the program includes Bernstein's Missa brevis, motets by Copland and - of course - Barber's inimitable Agnus Dei.