Perhaps it's a credit to the DS prop makers that they created such a realistic looking thing like Josette's music box and made it look so real. Even if the music box was real which I doubt, it never really played the music. All of that came from music supervisor Sybil Weinberger who was in the control room. (She later went on to marry producer Robert Costello) She selected all the cues to be heard that day, and they were then recorded on the audio track while the show was taping live. The actors by the way, could not hear the music while it was playing. That would have been too distracting.