Visible crew/equipment: When Johnny is spinning the two robbers around, you can tell that he is actually holding dummies. In the close up shots of the robbers, you can see them kicking their legs, but in the wide shots of the room, they are rigid and lifeless.
Visible crew/equipment: When Fred is chucked on the table and says, "Watch the silk." you can see that its Fred's stunt double as he's a lot fatter and his hair is obviously a wig also he does a really good job of covering his face so the audience can't see hes a stunt man.
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