Am I the only one who thought Johnny Depp & Helena Bonham Carter had weak singing voices in 'Sweeney Todd'?

Johnny Depp is a singer he used to be in a band until his good friend Tim Burton suggested he pursue an acting career. I thought he did good a very good job for how long he had set singing aside. Helen Bonham carter isn't a singer i don't think. her voice did appear to be much weaker than others in that movie. they may have tuned her voice in editing which would make it sound weaker.