On 24 December 1781, in the outbuildings of Emperor Joseph II’s Viennese Imperial Court, Mozart and Clementi faced each other in a musical duel. The extant documentation allows this confrontation, brought about by the Emperor himself and in which both of the composer-performers were required to improvise at the piano, to be partially reconstructed. A few months later, Mozart composed this Fantasia, which reflects all the elements typical of an improvisation and might even have formed part of this duel: arpeggiated chords, rests with dramatic effect, changes of tempo and fragmented melodies.