FOLLOWING HIS OSCAR-WINNING Johnny Cash biopic Walk The Line, co-writer-director James Mangold carried over one mandate for new Bob Dylan biopic A Complete Unknown. “I expect my actors to play and sing live on camera,” he says simply. So, while in wide shot or seen from behind, Timothée Chalamet, who plays Dylan, could mime along to the track — but when the camera was on his face, the actor had to do the singing and guitar-strumming thing for real.