This is brilliant, and you NEED to check it out right now. Microsoft Research has produced software for your computer called Songsmith that automagically generates synthesised accompaniment to songs that you sing into it. Or, more amusingly, to famous songs that you play into it. There are a number of these now cropping up on YouTube, and someone called Tim has produced most of the good ones so far. Here are a couple of my favourites: a techno version of Oasis’ Wonderwall and a latin version of Roxanne by The Police. Enjoy!