I love bluegrass but I have yet to hear much of what you're talking about. Care to name a few artists?
Roscoe Holcomb, Dock Boggs, Vernon Dalhart, Memphis Jug Band. I am lumping some stuff together I know but this thread is better off being a blanket 20-30s folk thread.

You can probably get at least an idea of what I am talking about by watching the movie O Brother Where Art Thou?, it is full of this kind of music.

Idk that much though, like I said at the start I am just getting into this kind of stuff but I find it to be really cool.