Cosi fan tutte, or "la scuola degli amanti", is an "Opera buffa", or in the german original language, "Ein Komisches singspiel" in two acts, with an italian libretto by Lorenzo Da Ponte. It is the third collaboration between them, and the last one. The work was premiered on the 26th of january 1790 in Vienna. Besides the impressive "buffo" Arias like "Non siate ritrosi", there is in this work a peculiar mixture of "opera Buffa" and dramatic content: in the quartet in A flat of the second finale the three lovers sing a luminous canon, while Guglielmo, the "left out", makes furious comments. In the quintett "Di scrivermi ogni giorno", the quartett unfolds beautifully while Don Alfonso retains from laughing. These oppositions give a deeper insight into the characters.