there's some humor in music. a lot of talented musicians prefer to go the route of tragic music instead, either in the pursuit of trying to come off as "deep" or because they just feel more touched by music when it's sorrowful than music that's funny.
also of course a lot of the music/art snobs out there will decry any humorous music as low art, which IMHO just proves that they're personally of low intellectual standing.
I've been listening to some of Ween's stuff lately... stuff like "Where'd The Cheese Go?" and "Mister Will You Please Help My Pony." It is utterly hilarious, and it takes a lot of creativity to a) come up with the concepts of those songs becuase they are so damned ridiculous and b) still make them fun to listen to.
There are also bands like Primus, whose music is often very "silly" though i don't quite like using that word to describe it because it seems to put it in a more childish light. songs like "Winona's Big Brown Beaver" have an obviously humorous context, and it's made funnier by the fact that despite the sexual overtones, the song
really is about a beaver owned by a girl named Winona. But then there are other songs like "My Name Is Mud" and and "Puddin Taine" which are still fun songs to listen to although they aren't outright funny, and they're also all technically brilliant and creative in a way that many musicians only wish they could touch.
There's also Tenacious D, whose songs like "The Greatest Song in the World (Tribute)" and "F--- Her Gently" have wound up on the iTunes of every other person in college in the US. Just last night I downloaded the Frank Zappa song "Valley Girl" he did with his daughter, Moon Unit Blue Zappa (i only did this because no one had the CD

). And then there are bands like Manowar, who are inadvertently absolutely friggin hilarious.