How little I know...
I have been guilty of post hoc ergo propter hoc reasoning.
I assumed that the rhythmic emphasis on the second and fourth beats in bluegrass and country music arose out of the similar emphasis in jazz -- boom-chucka, boom-chucka. How wrong I was...
In my research for this book I've been listening very hard to a couple of collections of very early country recordings, "The Stuff that Dreams Are Made Of," a set of extremely rare 78s of blues and proto-country; and Harry Smith's magisterial "Anthology of American Folk Music," which was perhaps the most important factor in the rise of the folkie movement in the late 50s and early 60s.
These records are, needless to say, astonishingly evocative.
But the most amazing thing about them is that it becomes instantly clear that country music had that boom-chucka beat long before jazz was a factor in rural life. If I'd thought with any clarity about it, I could have come to this conclusion without immersing myself in these collections; I'm not unacquainted with these tunes.
What bluegrass did was not to appropriate a rhythm from jazz; what happened instead was it took that rural dance-beat, and sped it up and gave it that wonderful drive that makes it such a compellingly toe-tapping medium, where the banjo is free to do all that great riffing a good picker can do.
(No insignificant thing, that fifth string. I'm doing a whole chapter on it.)
So the question becomes, When did this music acquire this beat? You don't hear it in "authentic" recordings of Celtic or even any other European folk music -- not so far as I can tell, anyway. Is it African? More listening sessions in store, methinks....
Another stunning thing is how much larceny went on in the first half of the twentieth century. I'll be humming along with Dock Boggs' "Country Blues" (1927) and it will suddenly hit me: Bloody hell, that's "Darlin' Corey"! Up comes John Byrd's "Old Timbruck Blues," and it becomes eminently clear where Bill Monroe "acquired" "Molly and Tenbrooks."
This is capital fun. Why didn't I think of this unemployment dodge earlier?