Zachriel brought up the closing song to "A Mighty Wind" with its risque joke - exactly the sort of thing an earnest folksinger might have unintentionally missed at the time, or a smirking one done on purpose. On my only viewing of the film, I thought the dialogue and situations clever, with some holes. I was uncomfortable with the songs because I actually sort of liked them, and felt I was being made fun of myself. I mentioned this again years later. I wrote songs like this, and certainly sang many more. I like to think I had some perspective, even as a twenty-year old, and wouldn't be that far over the top, but...then I remember what I actually did sing, with my little cheat-sheet of the order of the set taped to the top of my 12-string. I didn't write any coal-mining songs, nor perform any I can recall. As a northerner playing in the south, I knew I didn't have the cred for that. OTOH, I sang lots of songs I didn't have the cred for.
Since seeing the movie I have gradually reversed field. The scenes and dialogue are a pretty good sendup, but ultimately, they are an oversell. But the songs. They got those right. I now think they got them just close enough for pain. Brilliant. Easy enough to imagine the Kingston Trio singing this. Now imagine Pete Seeger singing a slightly different, "more authentic" version.