What happens when you 1) were thinking about stupid songs that you can't get out of your head, 2) are listening to the audio of Jimmy Wales talking about Wikipedia in Boston (audio and text transcripts here), 3) are chatting to wikipedians on IRC and 4) happen to have Garage Band open? This (800K mp3 / 870K ogg).
PS I would like to add that many wikipedians contributed links, sounds and feedback in the creation of this piece. It's amazing what you can do as a community. ;-P Just kidding, I can not take credit for the entire work, but I have no one to blame but myself.