Rock star in chains

Trying to find name of a movie from late 60s early 70s. Remember a scene where rock singer is brought on stage in a cell with chains on his wrists. Sings to audience to help him get free. Back stage, still in chains while his managers are in conference. Talk about how he made a commercial for Washington apples and sales rose incredibly high. When he was finally free, all existing film of him had sound removed.