I don't think this one has been mentioned before. Apologies if it has. However, Prison Worksongs LP Collector JGN 1006 consists of field recordings made in the Louisiana State Pentientary, Angola made by Harry Oster about 1959. The disc also appeared on Oster's own label (Folklyric?) before being reissued by Chris Strachwitz. The tracks are currently available on Prison Worksongs Recorded at the Louisiana State Penitentiary at Angola, L.A. Arhoolie CD 448.