There is one bonus featurette on disc 1 of SWEENEY TODD. It's a real making-of documentary (the one on the second disc was fluffy electronic press kit kind of stuff) that runs almost 30 minutes. We see them recording the score, we see them rehearsing on the set, and then filming in small bits.
During this feature, it came out that Helena Bonham-Carter wanted to play it bigger, and Burton wouldn't allow it. He wanted her performance internalized and quiet so she'd be inhibited in the same way Sweeney was. At least now I know who to blame for the only performnace in the film I didn't care for.