Hark! Their voices weave and flow as one in mysterious harmonies, shrouding the identity of each as they deftly shift from part to part. They are, of course, Anonymous 4, the vocal ensemble whose repertoire runs from medieval gems to traditional American ballads and works by singular contemporary composers Peter Maxwell Davies, John Tavener, Steve Reich and Richard Einhorn. The very visible members are Californian Marsha Genensky and New York residents Ruth Cunningham, Susan Hellauer and Jacqueline Horner-Kwiatek. This week they bring to the Kennedy Center a Christmas gift of carols and ballads inspired by “The Cherry Tree Carol.”

One of many such carols sung at religious events or to teach a moral lesson, it emerged in the British Isles during the 15th century, composed by Franciscan missionaries who had been traveling there for 200 years to spread Christianity.