Jennifer Lopez has an early holiday gift for you. The ever-hustlin’ 51-year-old joined her friend and vocal coach Stevie Mackey for a track on his new album “The Most Wonderful Time.” She duets with him on the record’s seminal song, of course, lending her pipes to “It’s the Most Wonderful Time.” It was a special collaboration for Stevie, who’s served as a coach on NBC’s The Voice for over ten seasons.