I came across this site, and thought this was fun, I always had this idea, and somebody did it, nayio.com has started a new service called Humming Search
Humming Search

The concept is really simple, all you have to do is hum a few lines, and it will give the info on the song, It works only in IE so far as it uses a ActiveX control. The service was good for a new one. I think it needs lot of refinement, but hey we all know how good is speech recognition. If get a hit you will get link redirecting to napster, where you can listen or buy the song. Well I tried few songs but no hit, but surely after refinements this will be a great tool. But it still can't beat asking your friend.