I've gotten much more done with this one than anything else: http://www.youtube.com/watch?v=tfPHEUZbPnw http://www.youtube.com/watch?v=tfPHEUZbPnw An hour long

I've gotten much more done with this one than anything else: http://www.youtube.com/watch?v=tfPHEUZbPnw http://www.youtube.com/watch?v=tfPHEUZbPnw An hour long of unchanging audio sort of fades into the background so you are unaware of it.