Speaking of the 1976 production, there's a great recording of it, and, to my ear it's the most satisfying recording of them all. It was done by the Houston Grand Opera, conducted by John DeMain, and last time I looked, it was still available as an RCA CD. Also of interest is a recording of members of the original cast (Todd Duncan and Anne Brown) and of the B'way revival cast, in 1940/42 (currently available as a Decca CD and as a Naxos CD).