Holiday classics get the big-band treatment, with nods to the Rat Pack. When Brett Eldredge decided to make a swingin’ Christmas album in May, the country star hung Christmas lights all over the studio to get his band in the holiday spirit. It worked. “Let It Snow! Let It Snow! Let It Snow!” has the same soulful essence of Sinatra’s version from 1948, and “Baby, It’s Cold Outside,” a tender duet with Meghan Trainor, is so pure it feels plucked right out of the '50s.