A visit with this wonderful chamber choir, directed by Marie Caruso, has become a seasonal tradition for our Downtown Music audience. This year, they offer the 13th-century conductus "Exultemus et letemur," Dufay's "Ave Regina caelorum," and the Spanish villancico "Dadme albricias," as well as a premiere by Erik-Peter Mortensen, 'All Hail!' The Bells of Christmas Rang. A conversation with Marie Caruso, Erik-Peter Mortensen and Tim Lewis follows the program.