This was my first memorable exposure to Aretha Franklin (also - this movie is incredible in every way)
Shooting that scene was an absolute nightmare for the director. Because Aretha never sang a song the same way twice. She was always riffing on the words, and structure, and playing with it. But they needed her to do it the same way several times in a row, to get the multiple camera angles and shots they needed to make the scene work. The director, John Landis, would get a shot, and set up for another angle, and then tell her to do it the same way, and she couldn't remember what she'd done in the previous scene. She just sang every song honestly, heart-felt, and completely in the moment. And then later on, when asked to reproduce the same thing, she was at a total loss because she was no longer in THAT moment. She was a wonderful artist. Side note: Back in the 1980's I was in a band with some famous people. We were going into the recording studio, and there was a chance that Aretha was going to come and guest on one of our songs! She was supposed to be in San Francisco (where I lived) for a show, but this was during the era where she was afraid to fly. Unfortunately, the logistics of getting her from NYC to SF for a show was just too much, and her appearance was cancelled. So we didn't get to record with her. And since we were kinda nobodys, and it was the mystique of Aretha that got us on the schedule in the recording studio, our time was bumped and given to someone who could pay more for it. So that band never committed anything to tape. :-(