The problem is that it's so jarring to hear his magnificent singing voice arising from an animatronic monstrosity... especially since he doesn't do the character Tennessee's dialogue (Tennessee sounds like a hick when talking) but just the music.

This clip shows them very briefly, but sadly the dialogue at the end was cut out. You do get to hear Don sing as Tennessee.

[ame]http://www.youtube.com/watch?v=JhI7C1Ha_pk[/ame]