In this column: blues enthusiasts, folklorists, musicologists, Harry Oster, Stefan Wirz, Butch Cage, Willie B. Thomas, Lawrence Gellert, negro songs of protest, Heritage Records, Bruce Conforth, unknown prisoner performing Mr. Tyree, Bruce Jackson, On the Inside, Pete, Toshi and Daniel Seeger, Afro-American Work Songs, Sam Charters, Fury Lewis, Sleepy John Estes, Ann Charters, Singing the …