Holy cow, this is neat.
Someone developed way to help you identify a song if you don't remember the words.
Here's how it works: You visit SongTapper.com and tap (with any letter on your keyboard) the lyrical beat of a song. For instance, you don't need to remember the Beatles song goes "Yesterday... All my troubles seemed so far away." You just need to know it goes: "Yesterday... Nah nah nahnah nah nah nah nahhah."
Tap the lyric beat for a line or two and SongTapper will show you a list of possible matches. If it doesn't find a match (and assuming you know the name of the song) SongTapper asks you to enter the information, thus expanding its (ever-expanding) database.
(The SongTapper requires the free Flash player plug-in. If you don't have it, it'll point you in the right direction.)
Give SongTapper a try. It's a pretty neat invention.