As I mentioned in my last post, this is a great cut of Muddy and Sonny Boy Williamson, with Willie Dixon on bass and Otis Spann on piano doing Got My Mojo Workin'. Notice the style of the players and the especially the conk on Muddy. Also, check out the audience in the last shots.
All three DVDs of The American Folk and Blues Festival are full of classic performances like this one. Available from Amazon.