When singer India.Arie and pianist Joe Sample invite friends over for a bit of Christmas cheer, they don't fool around. Yacht-rock legend Michael McDonald and a big band send "Merry Christmas Baby" into the stratosphere, while Take 6's Khristian Dentley helps unearth the medieval mysteries behind "God Rest Ye Merry Gentlemen." Best of all, on "Favorite Time of Year," Arie and Tori Kelly reel off the moments—from sweet-potato pies to "Tyler Perry's new movie"—that make the season so special.