A while ago I found a website that allowed you to enter a word, sentence, etc... and then it would generate a sound clip that used various lines from songs to essentially say out those words. It was a very interesting web app and I have had little luck finding it in Google again.
While I think this question is out of the scope of Webapps, the tool sounded interesting so I did some research.
Is "Let them sing it for you" the tool you're looking for?
Looks like the original creator has stopped hosting the project:
For unknown reasons the Swedish National Radio decided not to host the project anymore in late 2011. Hopefully it will be up soon again.
There is a Chrome Extension that still lets you do this however. I will not put the link here because you should always be wary of installing extensions from untrusted authors. But if you want to investigate and give it a try, search for "Let them sing it for you" in the Chrome store under "Extensions"