Check out the last few recordings by Joan Baez. I think it shows up on her album "Recently" but it might be on another one... she sings it beautifully and I suspect there may be some useful info' in the liner notes. She might even have written it. She talks a great deal in her autobiography about time spent with/around Martin Luther King Jr., and she was once asked to sing a song to wake him up when his friends needed to consult him but recognized his exhaustion from "the good fight."

Good luck with your search,

--Cuilionn