Young Gifted & Black.
Aretha, Chuck Rainey, Cornell Dupree & Purdie cut Rock Steady with Gene Paul (Les' kid) engineering when Wexler & Ahmet Ertugen went out for lunch.
When they returned, they heard the tune and tried to re-cut it, so as to claim some production credit, but according to Chuck, they never could get that feel again, so the demo the folks made went onto the record.