Watch the The Rag Trade online guitar lesson by David Hamburger from New School Fingerstyle
The second section of "The Rag Trade" combines a rumba rhythm in the bass with some descending sixths on top, all of which I cheerfully stole from Jellyroll Morton's "Mamanita." But I'd heard that sort of thing earlier, and more guitaristically, on Ry Cooder records from the 1970s like Paradise and Lunch and Boomer's Story. Then again, you can hear the same kind of things in Professor Longhair's music. Jellyroll Morton called it "The Spanish Tinge," declaring it an essential jazz ingredient in the 1920s. Hmm.
Reference Source: Professor Longhair (http://www.coldbacon.com/music/fess.html)