Summertime Blues I saw Blue Cheer in 1970. It was absolutely the loudest band I have ever heard and and I have heard Deep Purple and Emerson, Lake & Palmer. Talk about heavy metal. They were on a proscenium stage and there was a solid wall of triple-stacked Marshall cabinets behind them and three racks of amps. The building shook. The air moved when they played. Our ears rang for a week.
One of the great things about Rush - and there is a multitude - is their ability to sound like "a bunch", when there's only three.