Watch the movie to then end where they are having the talent contest. As the main character, played by Michelle Pfeiffer, kneels down to sing her solo, look at the girl in the background dressed as a wine glass with fake legs hanging out of the top. Instead of singing the song, she's just opening and closing her mouth.
I would have to go back and watch again to make sure, but if it is when Michelle Pfeiffer kneels down to sing her solo, the others stop singing. Maybe the girl in the back is chewing gum or something.