Lomax field recordings
Ralph Rinzler field recordings
The Lomax collection is from the 1930s and contains unaccompanied singing. The Rinzler recordings are from the 1960s and are mostly band recordings. Four cuts consist solely of Edius Nacquin, accompanying his voice with fiddle. There was once a second volume of Rinzler material, but it seems to have disappeared from the catalog (possibly cannibalized for other compilations).
Worthwhile notes in both collections, especially the Lomax