That's fascinating... I've never even heard of livecoding. Definitely going to have to play with this a bit. And it's motivation to learn Lisp.
As to the video, I really wish the music was louder. Hard to hear when the narrator's voice is so much louder. (I've also got background noise to listen through).
Trust me, Impromptu does not need a narrator to speak for it.
Too bad Sorenson has no plans to port it to *nix ( http://lists.moso.com.au/pipermail/impromptu/2007-October/00... ).