Although most of the cast do their own singing, Jake's singing voice was provided by Zachary Throne and Mark's by Barry Coffing.
We've got good news, we've got bad news, we've got worst news.
Tony: The good news is everyone likes our song.
Sly: The bad news no one believes it's ours.
Jake: And what's the worst news?
Tony: THE GIRLS ARE COMIN'!