-DISCLAIMER-
I am not a lawyer, The following is stuff that I have learned because I have had to go through the process of getting licenses for the songs I record.
-END DISCLAIMER-

In the USA (and I am assuming that since your replicator is in Minnesota that you are in the USA) It's pretty much standard op procedure now that you do have to be able to produce proof that any songs you are recording commercially are either in the PD or that you have a mechanical license granted to you.

You might contact the American Folklife center at the Library of Congress to start. Stephen and Jennifer are amazing in their knowledge and if they don't have an answer might be able to point you in the right direction.

You might also do a search for copyright on Harry Fox, Inc. They represent a bazillion publishers of composed music and it's always worth it to pay the fee just to be legal.

In my own experience, I recorded a 130 year old song that is still under copyright, but ONLY the sheet music. I consulted a lawyer and they said that since I learned the song through oral tradition, that I was in the clear since that version had significant changes from the original. This situation might also be so in your case, but please don't bank on it.

If what Bruce gave you above doesn't help (he is also pretty knowledgeable about this stuff) there are also some very accessible blues folks who might be able to help you: Andy Cohen and Scott Ainslie are the two that immediately come to mind. You can Google them both. My money would be on Andy. he's amazing in the stuff he knows. Send me a PM and I'll put you in touch.

Hope this helps,
Deb Cowan