(YouTube link)
Released only a couple of weeks ago, Microsoft Songsmith takes your singing and creates a somewhat workable tune around it. YouTube users have fun with it by entering a cappella versions of hit songs to see what music Songsmith comes up with. The results are hilarious, like this cruise ship version of Roxanne by The Police. Pitchfork has a collection of precious Songsmith remixes, with songs by The Cars, Radiohead, The Doobie Brothers, Van Halen, and Oasis. Link -Thanks, Ron!
But, generally, the problem with songsmith is that it doesn't vary it's melodys enough. Unlike this song, most of the ones I've heard it just plays the same melody in a loop under the lyrics.
I feel like I'm in a David Lynch movie listening to some of them.