 DATE: In one scene, Baron Gruner is listening to a recording of a  baritone singing the "Madamina" aria from Mozarts "Don Giovanni",  and the singer is backed by a full orchestra. Such recordings were  impossible to make in the nineteenth century, when the story takes  place. Until the advent of electrical recording (i.e., using  microphones) in 1925, singers and instrumentalists had to stand  around a large horn to make recordings, and the use of a large  orchestra would have distorted the sound. Special "chamber music"  arrangements had to be made of orchestral pieces to prevent  distortion and overload. Recordings were made on wax cylinders then,  not discs, and the quality of sound was far worse than demonstrated  in this episode.