Mozart left Prague for Vienna in November 1787. Music lovers in Vienna had heard good reports of "Don Giovanni". The Emperor ordered the opera to be produced at the Burgtheater. Mozart wrote some new music for the characters of Elvira and Ottavio. He also wrote a duet for Zerlina and Leporello. "Don Giovanni" was first performed in Vienna on May 7, 1788. Mozart's sister-in-law Aloysia Lange sang Donna Anna.