Humor in music is hard. It's easy to be downright zany, but difficult to be humorous in more refined ways. The most common musical humor is probably subtle mockery of figures or styles, like the little pop figuration by Busoni in his Sonatina ad usum infantis (just into section V: Polonaise un poco ceremonioso). My favorite type of musical humor, though, is the grotesque, with its sinister undertones, but my comedy of choice is dark and dry. My appreciation of Shostakovich is mostly along those lines, and, to some extent, Alkan.