"I did some lessons with a voice coach because I can't sing. There were 100 extras and John [Maybury, the director] was like, 'Now you're going to sing...'," the actress recalled to Total Film, contactmusic.com reported. "I've never been so frightened in my entire life... I don't know how singers do it. I never want to have to do it again. I don't want to be a rock star."