Factual error: When Johnny shoots the taxi with some kind of cable and pulls it backwards, the rear tires are shown to be spinning in an attempt to move. The taxi is a Chrysler K-car which is front wheel drive.
Factual error: The movie is supposed to be set in the USA, but throughout the movie you can see buses and trolleys from Toronto, Canada. Anyone who's been to Toronto or is interested in city transit could recognize it.
Answer: They could only communicate via musical tones. They were trying to give Sandy clues as to where they were being held (playing 'Downtown' to let her know they were downtown). 'Help Me Rhonda' was a clue that they were in trouble.
Brian Katcher