As one of music’s preeminent nice guys, John Legend is guaranteed to radiate warmth and sincerity on camera. He projects a rare humility when he foregrounds urgent social issues in “Preach” or when he celebrates the beauty of the diverse array of women in “You & I (Nobody in the World).” While Legend may prefer being earnest and emotive whenever he’s the focus, team-ups with Benny Benassi and Tiësto prove he knows how to have fun, too.