The Library of Congess has many collections of field recordings, e.g., the 'Folksongs out of Wisconsin book' is only to top part of the collection. The Library of Congess has a duplicate of the whole collection, including field recordings. Many from these collections have been on 78s and LP's for a long time. AAFS 1 to 59 are the LPs. I have Rae Korson's undated catalog of these, c 1960.