Almost any thumbnail sketch of Mozart shows a genius composer who never missed a good party. One particular Carnival season had Mozart all keyed up. In the Catholic Austria of Mozart's day, Carnival, the weeks leading up to the beginning of Lent, was a time for all manner of merrymaking, especially masquerade balls. During the 1783 Carnival season, Mozart was planning big fun. On Jan. 22, 1783, he wrote his father, Leopold, from Vienna, "You are doubtless aware that this is carnival time and that there is as much dancing here as in Salzburg and Munich. Well, I should very much like to go as Harlequin (but not a soul must know about it) - because here there are so many - indeed nothing but - silly a--es at the Redoutes. So I should like you to send me your Harlqeuin costume." (trans. Emily Anderson) And Mozart was serious about his costume balls. He went on to write Leopold that he and Constanza don't go to public costume balls but instead prefer to attend private ones, like the one Mozart had thrown in their own home recently from 6 p.m. until 7 the following morning. And two weeks later, on Feb. 5, Mozart urgently reissued his request for Leopold's costume, writing, "I have received your letter and trust that in the meantime you have also received my last one with my request for the harlequin costume. I now repeat it, begging you at the same time to be so very kind as to dispatch it with all possible speed." It seems Leopold came through. On March 12, Mozart wrote his father of the Commedia dell'arte-style pantomime Mozart and his co-conspirators pulled off - presumably with Leopold's Harlequin costume. "On Carnival Monday our company of masqueraders went to the Redoute," Mozart wrote, "where we performed a pantomime which exactly filled the half hour when there is a pause in the dancing. My sister-in-law was Columbine, I Harlequin, my mother-in-law Pierrot, an old dancing master (Merk) Pantaloon, and a painter (Grassi) the doctor." And in case you're wondering, Mozart-the-great-dramatist confirmed the pantomime's originality, writing, "Both the plot and the music of the pantomime were mine."