John Jacob Niles NEVER claimed to be "authentic" in regards to his singing voice. That was the point.   In the 1930's, decades before the "Folk Era" (or "error" in some people's opinion), Niles was simply introducing songs, and creating songs, to bring to the attention of the general public. He was not collecting to preserve, just to create his own performance. The idea was to bring the music to the concert stage and elevate to the status of "art" songs.

In reality, how authentic did he need to be?   Is it considered "authentic" when a Jewish kid from the Bronx puts on an accent to sound like a Southern sharecropper?

I hope some of you had a chance to listen. I think Ron Pen explained Niles, warts and all, in his book.   The show is archived at www.wfdu.fm for the next two weeks.