While in Vienna, he also composed what are widely considered to be two of his greatest works – Mass in C Minor and Piano Concerto 21.
His golden decade in Vienna (1781–91) was marked by his three-opera collaboration with the librettist, Lorenzo Da Ponte: The Marriage of Figaro, Don Giovanni and Cos ì fan tutte represent the peak of his achievement in opera and, indeed, are the highpoint of eighteenth-century comic opera. While in Vienna, he also composed what are widely considered to be two of his greatest works – Mass in C Minor and Piano Concerto 21.