Isn't it all about music influenced by 'roots' styles - Bluegrass, Zydeco, Cajun, Blues? From memory, when I was working in the record business, there was an Alt Country movement - Steve Earle, Cowboy Junkies etc. a kind of antidote to the other development of the time, New Country. Alt Country then merged with other sub genres, a couple of big acts (Springsteen) went back to a more traditional sound, and a new marketing tool was born.