I am currently listening to Johnny Winter, Muddy Waters and B.B. King. I know, that these guys play very often together.
The last LP I was listening to was Muddy Waters - Hard Again from 1977. The opening song is Mannish Boy, which is a rerecording from the original one from 1955.
I know that Johnny Winters was the producer of Hard again, but: If you listen to Mannish Boy in the background someone is screaming "yeah". Is this Johnny Winter? The sound of the voice is very similar from the live recordings of Johnny Winter, but I can't find any information if he was also performing and not only the producer.