I noticed it too, like the howling on the train, Humphrey's voice is clearly Justin Long's, but when he howls during Kate's requiem that sounds like a real wolf!

ya i think thier both justins and haydens voice but when u hear justins voice u clearly know its him by the voice i guess it could be haydens to but when they sing it kind of combinds them and its hard to her whos who but i get what u mean

sometimes actors dont do the singing and they get someone els in, ive seen that a lot

I bet Hayden used her own voice to howl because she is a singer and has a beautiful voice!

true i just was thinking what anubis pointed out and i was hoping it wasnt cause then id have been disappionted

yeah it usually is, but it usually tells u online if u look up the soundtrack ur see who was singing

If that was Justin Long, then he got some skills!

idk i know justins a good actor but i dont think hes a singer he might still have a good voice though

Actually, since Justin Long voices and sings for Alvin from Alvin and the Chipmunks, then he obviously sings.