Played around a bit more and a plain 50Hz sound has a traffic of over 737 (again, Audiosurf gave me a different number each time, but it was consistently over 700). And it doesn't make your brain explode like the high pitched ones

Edit: Here's a 5 min file of the 50Hz sound, which apparently has an even higher traffic (highest I've seen on this was 818, average ~760). Enjoy, it's good for training. Not much in the melody department, though, I think I should work some more on the harmonies

Until then, I guess you won't be putting it on your iPod
http://rapidshare.com/files/93287158/50long.mp3