you can accomplish that quiet easy in Motion:
you need two layers, one for the head, one for the mouth (demands some cut&draw prep in Photoshop, Pixelmator etc)
then apply an Audio-Behaviour to the Y-axis of the Mouth-piece, have a look:
… that charming fellow is our schools name-patron, Max Planck.
see the Mouth-piece? And, more obvious the teeth and the black... I call that Python-izing, cause Terry Gilliam from Monty Pythons used this in extenso)
… unfortunately, I can not make it a universal-plugin, cause Audio-parameters can not been published (Top3 on my Wishlist, are you listening, Cupertino??!)