Yah when you're a DJ and don't have vocals you probably shouldn't sing an artist's song when they're hanging out at the club you're spinning at, unless you want to catch a couple side eyes and clowns! When Usher and Jermaine Dupri enter a club, the DJ almost always knows they're in the building so there's no excuse for this DJ's set...maybe this is his jam and he was just feeling himself, but from the look on JD's face he wasn't...LMAO!