In the spirit of the above, Cantlin Stone Free Festival 1983. I don't remember any of the bands (or if there were any) but I'm pretty confident I was utterly blown away...
Saw Here & Now supporting Gong in about 1994/1995. As far as I could tell the only visual difference was the Divided Alien when in Gong mode. Musically, Here and Now were in phenomenally tight jazz rock mode. Gong were, well, Gong... 🙂