1973 documentary of a memorial concert for the Watts riots, intercut with Richard Pryor monologues and man-on-the-street interviews. Jesse Jackson gives a call-and-response invocation at the opening. If you ever wondered how Rev. Jackson came to prominence, this will give you part of the answer. The rest is here.
Mel Stuart directed and David L. Wolper produced. That's right, the guys behind the original Willy Wonka movie. Stuart also directed the insane Running on the Sun, giving him one of the weirdest CVs in film.
Somehow I missed Wattstax when it was rereleased in 2003. It's got a spiffy new 5.1 mix, and if you like soul at all, you're gonna love it.