I don't think you understand my point about Woody, so I will say in another way, one more time, and then leave it at that--Woody's music used traditional/folk music for his songs, and he learned that music from those around him, who had learned it the same way. And writing topical songs, in the way that he did, is tradition, in and of itself.
How or why this makes ethnic music invisible is not clear from your post--
Anyway, I am not sure you are interested in eliminating and ruling out various kinds of music, what exactly is it that you are eliminating them from?
Most music has traditional and folk elements of one kind or another--even the genres that pops up one day and are gone the next--