folk-blues

Noun

 * 1)  A genre of blues influenced by early 20th century folk music.

Usage notes
Sometimes used more generally to refer to any style of blues that is traditional as opposed to popular music, though that is more often without the dash: folk blues. For example, the Piedmont blues is a folk/traditional style of blues but it is not influenced by folk music; thus, it is folk blues but it is not folk-blues.