Here's a big one to chew on, Supershow. Sound isn't great but it has its moments. Clapton, Stills, Bruce, Buddy Guy, The Misunderstood, Buddy Miles, Roland Kirk, Colosseum and the Modern Jazz Quartet. Shot in London in March of 1969, a two day affair. Shot in a discarded linoleum factory.
I believe that Zeppelin played but did not make the cut. The footage of Riverside's Glenn Ross Campbell and the Misunderstood is very rare. Around the 29 minute mark. Hell of a steel player. Leslie and I were lucky enough to see him play once with Love. Buddy Guy rips it up at the fourteen minute mark.