I remember hearing John Singleton mention that album in publicity press junket interviews, back when he got Williams to score "Rosewood" (after Marsalis was let go).
Oh yes, I'm well aware of JW's work with Mahalia Jackson. She was probably the highest profile "popular music" artist he arranged music for back in the day.
Obviously, Williams was under contract to Columbia Records at this point, where he arranged and backed other artists for the label, as well as releasing the "Checkmate" and "Rhythm In Motion" albums.
