my high school best friend's older brother, Rusty Brutsche, was one of the founders of Showco, the company which first built the sound equipment necessary to do those huge stadium gigs. That was in 1970. If you're interested, Wiki "Showco" for more -- it's an interesting story. Ten years later, the same guys started Vari-Lite and revolutionized stage lighting (if you've ever seen the Pink Floyd "Pulse" concert DVD, you know what I'm talking about). We all owe Rusty and friends a "thank you" for making many of our rock music experiences possible.