By the end of the 1960s, some rock bands were pushing volume, distortion and riff-based writing into a much heavier form. Blues rock remained the foundation, but the mood became darker and the sound more physical.
From blues to weight
Cream, Jimi Hendrix and The Who helped normalize loud amplification, while Led Zeppelin’s 1969 debut brought blues riffs, acoustic contrast and massive drum sound into a new scale.
Proto-metal ideas
Heavy riffs, darker lyrical imagery and extended guitar power were already appearing before heavy metal became a fully defined genre in the early 1970s.
Why it matters
Late-1960s hard rock created the bridge into Led Zeppelin, Black Sabbath and Deep Purple, establishing the sonic vocabulary that would dominate much of 1970s heavy music.