"Cue Scoble tears. This is one hell of a technology from Microsoft Research that I think will have a huge impact on how amateurs and hobbyists write music. The technology and software prototype is called MySong.
In a nutshell, the software records your singing (preferably in tune) through a microphone, and it systematically generates an instrumental accompaniment for your song. The quality is even comparable with a professional accompanist, not to mention the cost and time involved."