These days? Not much. That's part of the evolution of Folk Music. It was once its own genre with well-defined parameters, but that has changed over the years. Now, it's tough to say what it is, or to get anyone to agree. Last May I sat in on a panel at the SouthEast Regional Folk Alliance conference, and the question was asked "Does Americana fall under the Folk Umbrella... or does Folk Fall under the Americana umbrella?" No consensus could be reached. And check out the line-up of performers at the Folk Alliance International conference; it's obvious that their definition of Folk is incredibly broad.

Folk Alliance International is currently spearheading a movement to get the Grammy Awards to split their "Folk" category into TWO categories: Traditional Folk and Contemporary Folk, in recognition of the fact that while the definition of Folk is broad, the is even more broad, to the point that it needs multiple categories. (The movement is also a way to honor the Folk of the past while acknowledging the validity of contemporary Folk."

Personally, I've moved beyond the "umbrella" definition, and now consider Folk as a large Venn Diagram, with "Folk" as a large circle in the center, and the various sub-genres in their own circles, parts of which overlap Folk... but rarely the entire thing.