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In an interview with an Italian website, Deep Purple bassist Roger Glover spoke about the bands that defined the beginning of heavy rock. Here's what he said:
“The word 'Heavy' was very commonly used in the mid-to-late 60s. Heavy music. I mean, Hendrix and Cream were paving the way. The band I was in before Purple, we thought Heavy was just about having more equipment and playing louder. And that's not it. It's not the same thing, just louder. And I realized this listening to Led Zeppelin, especially Dazed and Confused and How Many More Times, that heavy wasn't about big, loud. It was about attitude. That was the key. And then Deep Purple came along. So that's what helped me define where I was going.”