This article deals with some of the initial problems facing a translator of Da Ponte’s libretto to Mozart’s opera Don Giovanni. The attention is focused on the musical rhetoric of the baroque period and the set of conventions that Mozart emulated in his musical language, creating a complex interrelationship with the verbal text. Since musical rhetoric was a semiotic system capable of communicating with the audience with or without the aid of the verbal text, the music can enhance, add information to or contradict the verbal text. The author wants to show examples of operatic situations where the translator’s knowledge of the musical semiotic system as it was used during the baroque period is essential to his success in finding adequate material in a TL text.