This is a club for enthusiasts of folk, blues, singer-songwriters, jazz or any other sort of vernacular music.
The only rule I stress is you have to know the difference between genuine folk music and folk-influenced indie rock/prog/dark ambient/what have you. That isn't to say you can't join the club if you like those kinds of music, you just have to be able to distinguish Woody Guthrie from Neutral Milk Hotel.
This isn't necessary to join, but you can include a list of traditional musicians you enjoy listening to, if you're so daring. Here are a few of mine:
The Tiger Lillies
Iron & Wine
Fire on Fire
Bread & Roses
Aaaaand, a .jpg to seal the deal.
So yeah. Members please.