The key to the Sabbath's early sound is Tony's guitar, and the story of why it sounded the way it did. Geezer's lyrics, screamed by Ozzy, added to the legend. Their music was born out of the Blues, and I don't believe they set out to be innovators, but that's exactly what they became, although it wasn't recognised at the time. In the late '60s the term 'Heavy Metal' didn't exist as a music classification, but, for sure, everything that followed in Heavy Metal was derived from that Sabbath sound.