From www.mutopiaproject.org

A Musical Joke (in German: Ein musikalischer Spaß) K. 522, (Divertimento for two horns and string quartet) is a composition by Wolfgang Amadeus Mozart; the composer entered it in his Verzeichnis aller meiner Werke ('Catalogue of all my Works') on June 14, 1787. The music is intentionally written to be funny, being liberally sprinkled with obtrusively clumsy, mechanical and over-repetitive composition, together with passages evidently designed to mimic the effects of inaccurate notation and inept performance. Commentators have opined that the piece's purpose is satirical—that " harmonic and rhythmic gaffes serve to parody the work of incompetent composers" -- though Mozart himself is not known to have revealed his actual intentions.
The above text is available under the Creative Commons Attribution-ShareAlike License ( creativecommons.org/licenses/by-sa/3.0/ ). It uses material from the Wikipedia article "A Musical Joke" ( en.wikipedia.org/wiki/A_Musical_Joke ).