This isn't new, but I find I return to watch it often enough that I ought to share it with those who maybe haven't seen it at all.

In this video, Imogen Heap, an artist of sorta electronic pop music, performs one of her songs totally live and a cappella, laying down tracks and basically singing a really cool round with herself. Check it out:

If anyone knows where I can find a higher-quality version of this, I'm all ears!