What happens when one of the world's biggest music stars is unable to play at a major charity gig? He asks his famous mates to step in. U2 front man Bono was due to perform with his band at the World Aids Day RED Concert but sadly he is still recovering from a recent accident. But luckily Bruce Springsteen and Coldplay's Chris Martin stepped in. The two rock legends joined the rest of U2 on stage to perform with the band at the charity gig held in New Yorks Times Square.