Like Roger I'm not really interested in the "genre" and I find the blues as a subset of folk argument spurious at best. Blues derives essentially from African song and is that "folk" by many academics' definitions?

I'm sure that it's not your intention, but you give me the impression that you think of "folk music" in narrow, and perhaps, racial terms. The blues, most definitely, are derived from folk traditions. So, for that matter, is much African music.