to be fair, I went looking for an article or something along those lines, and scored a hit....
Robert Johnson - Steady rolling Man
This article goes through the theory, has some clip examples, and of course, as I look at the page, they are selling the album of slowed down songs for 4 pound.
Eh, I can do that with my own CDs and cooledit - which I did for crossroads.... to me it sounds just like a slowed down song.
I still have my doubts - only because it has never been brought up (afaik) till now.