This a cappella vocal quartet brings their exquisitely blended voices to the Music Room in Sing Thee Nowell, a program of sacred Christmas music spanning seven centuries. The Rosen House, splendidly decorated for the holidays, will be open for self-guided tours between the two performances. Ring in the holidays with New York Polyphony’s “rich, natural sound that’s larger and more complex than the sum of its parts” (NPR).