Who did the namesakes' singing voice in the movie "Dewey Cox"?!

Question: Who did the namesakes' singing voice in the movie "Dewey Cox"!?

I know John C!. Reilly PLAYED Dewey Cox in the movie, but it's hard to believe that he sung the songs in it!.
Please help!.!.!. =)Www@Enter-QA@Com

Answers:

John C!. Reilly sang the songs as well!.Www@Enter-QA@Com

Believe it or not it was all him!.Www@Enter-QA@Com

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