This popped up on my ewetube, unfamiliar with the harmonicist. One of the most hauntingly beautiful movie themes ever written; I need to watch the flick one of these days.
Janis Ian (still in her mid-twenties at the time) wrote this song and then collaborated with Phoebe Snow and Odetta to perform and record it. The album "Aftertones," which contains the original track, was released in 1976.
Years have passed now, but this song (in spite of the name, not at all religion-focused) is timeless and I daresay definitely resonates with many older listeners: