Did anyone notice this about the Saga? When Bonasera is telling his tale of woe to Vito, Vito answers by asking him a couple of questions. The first one is "why didn't you come to me first?" Vito's voice sounds quite different from the rest of the film. It sounds like they used a voiceover for Vito's first few lines. What do you think?
Could this be the result of sound editors trying to mask the cat's loud purring over Brando's actual voice? Perhaps they did have someone else voice over Brando's lines?