Jay Z surprised fans at his wife Beyonce's New York concert on Monday night (05Aug13) when he joined her on stage to close out the North American leg of her Mrs. Carter World Tour. The Crazy In Love hitmaker capped off three nights at the Barclays Center by performing her new, unreleased single Bow Down/I Been On before bringing the 99 Problems rapper out onstage, much to the crowd's excitement. The superstar couple performed Tom Ford from Jay Z's new album Magna Carta... Holy Grail. Beyonce is an uncredited vocalist on the track. The gig was the third of three concerts at the Barclays Center in Brooklyn, which Jay-Z's investment helped to build.