Perhaps the radio version you referred to, Joe, was what I remembered as "a 30-minute film." Could it have been sung by Paul Robeson in the NBC radio drama?

BTW, I've been searching the net for info but haven't found a MIDI (for others--I know the tune and the chords) or info about Robeson or Millard Lampbell or about the radio broadcast. I wonder if an audio of that broadcast is still available. NPR seems at least to have got hold of the longer song.