May I please add a related question?

As I recall, there was a version of Amazing Grace that became a mainstream radio hit in the late '60s or early '70s (no, not Scotch on the Rocks, nor yet Judy Collins). It was sung to the usual tune, but it had a much more interesting harmony than the one I'm stuck with on Sundays (from the Episcopal Hymnal). It was kind of bluesy. Can anybody point me to what it was?