Jim,
You said to limit the discussion to proper names and terms that are relevant to folk music. Not sure, from your wording, whether folk music terms that are not proper names would count, but here's one of my pet peeves--thanks to Bill Gates [i.e., Microsoft Word]:

"sing-a-long" -- which suggests one is incanting a lengthy ballad

The correct hyphenated spelling is "sing-along," meaning, of course, to "sing along [with] others. ["Singalong," without the hyphen is also acceptable.] However, Microsoft Word's Spell Checker program incorrectly 'corrects' you if you spell it correctly, and tells you it is "sing-a-long." Since Word is so widely used, the misspelling has become rampant.