My soft spots for Frank Capra and for group singing intersect each year with the Music Box's Christmas double feature and sing-a-long, Dec. 19-24. Tickets are on sale now. Per tradition, the movies are "White Christmas" and "It's a Wonderful Life," and each showing is preceding by a round of Christmas carols, led by Santa Claus himself. Related: This will be the last Christmas for Music Box managers Chris Carlo and Robert Chane, who after 20 years have handed the reins to their landlord, who promises to maintain the theater's format and physical layout.