These audio files are just a few examples of the 100's of recordings available as part of
*** The John and Ruby Lomax 1939 Southern States Recording Trip ***
At the time these were downloaded (April 2014) it was possible to retrieve these MP3s from this fairly low-tech site:
http://memory.loc.gov/ammem/lohtml/lomaxbibAudios1.html
These recordings may have moved as the Library of Congress is upgrading its archives.
Also see:
From http://en.wikipedia.org/wiki/Ruby_Terrill_Lomax#Field_recordings