Berlioz’s exquisite adieu ushers in carols, fantasias on Christmas themes and Handel’s rousing chorus. There are the sound of sleigh bells and whipcracks in Prokofiev and Leroy Anderson’s high-speed rides but also the hushed reverence of music for choir alone. With audience participation and some surprises along the way the final Saffron Hall concert of the year is the perfect way to Wish You a Merry Christmas.