Smithsonian Folkways has announced the forthcoming release
of recordings made by Mack McCormick:

Folkways - Mack McCormick Playing for the Man at the Door

On August 4, Smithsonian Folkways will release Playing for the Man at the Door: Field Recordings from the Collection of Mack McCormick, 1958 – 1971, a compilation of previously unheard field recordings from Robert “Mack” McCormick's legendary blues archive.

See also the Mudcat thread for Robert Johnson"

https://mudcat.org/thread.cfm?threadid=172152&messages=4

Thomas.