This was the first opera performed by Schikaneder's troupe at their new theater, and established a tradition within the company of fairy-tale operas that was to culminate two years later in Mozart's celebrated opera The Magic Flute. Oberon is similar to The Magic Flute in its plot and characters, and a number of the singers who participated in Oberon took similar roles in the later opera. As Giesecke had not acknowledged his debt to Sophie Seyler, he came under criticism for plagiarism. According to Peter Branscombe, "it has long been recognized that Giesecke, the named author of Wranitzky's libretto, deserves little credit for what is largely a plagiarism," concluding that "Giesecke's Oberon, König der Elfen is hardly more than a mild revision of Seyler's book." In later work, Giesecke translated the Italian libretti of Mozart's operas Le nozze di Figaro (1793) and Così fan tutte (1794) into German. In total he was to write libretti for more than fifteen operas by various composers between 1789 and 1800; see listing below. As an actor, Giesecke is remembered for having been in the cast for the premiere (30 September 1791) of The Magic Flute. He played the mostly speaking role of the First Slave. Later in life, he was said to have claimed to be the author of the opera's libretto, which is usually attributed to Emanuel Schikaneder; see discussion below. During his Vienna years, Giesecke became a Freemason, joining "Zur gekrönten Hoffnung", the same lodge as Mozart. He is believed to have been the librettist for the "Freimaurerkantate" Laut verkünde unsre Freude, KV 623 (1791), a work written for and performed at a Masonic celebration just as Mozart's final illness was setting in (see Death of Mozart). The head of Giesecke's lodge was Ignaz von Born, a distinguished scientist who specializations included mineralogy. Other eminent mineralogists were also members of the lodge and Giesecke's membership evidently rekindled his interest in the subject. When Giesecke ultimately departed from Vienna (1800), he did so under a shadow and perhaps in a hurry, as surviving court records show proceedings against him for non-payment of a year's rent. Personal effects he left behind were sold in 1801 to help cover this debt. As mineralogist The departure from Vienna coincided with a major career shift: Giesecke abandoned the theater and switched to mineralogy and mineral trading. In 1801, he studied for some time with Abraham Gottlob