Wow! I saw that same show. I was pretty young so we didn't drive. We took the train up from Chicago, planning on camping on the summerfest grounds (you could do that back then). JoJo Gun, then HP. They were good. But then the riot. People piled chairs and set them afire. The grounds and harbor were littered with empty beer kegs. Saw one thrown through a truck windshield. After the riot the cops came through with billy clubs swinging, even beating on the heads of people in tents. We got the he** out and spent the night in some thick bushes in a traffic circle in downtown Milwaukee. Tales of my youth.For maybe 10 minutes. I saw them at an outdoor show in Milwaukee in the '70s. I think it was called Summerfest??? Went up there from Chicago with the drummer in our band in what I eventually found out was a "borrowed" van. If I remember correctly, shortly into their set someone threw a hammer, or maybe it was bottles onstage, they walked off, and basically a riot ensued. When the police were clearing out the audience and said move this van now I was only one straight enough to drive it. We left without the drummer. He spent several days in jail. I remember absolutely nothing about the actual performance by HP. I never saw the drummer again.