The 1960s is one of the greatest eras in music history. The transformative decade saw a subdued ‘50s style evolve into the most experimental decade in rock, eventually setting the stage for heavy metal’s birth in 1970.

Without bands like Deep Purple and Led Zeppelin writing classics centered around heavy riffs, Black Sabbath (as we know them) may have never existed. Ritchie Blackmore was one of the fiercest guitarists of his time, bringing “Mandrake Root” down to the lowest note of E standard tuning. Jimmy Page was also brutally heavy for the time, almost reaching sludge territory in “Dazed and Confused.”

The Beatles invented so many sub-genres of rock, it could be taught as a college course. Many point to “Helter Skelter” as a proto-metal song, but more should acknowledge “I Want You (She’s So Heavy)" as the advent of doom. The song’s outro blew minds in the late ‘60s, using the same progressions Tony Iommi would later adopt for his riffs.

We also dug into some lesser-known gems for this list. Fat riffs from bands like High Tide, Jacula and Andromeda will show exactly how deep occult rock went in the underground.

Check out our picks for the 15 Heaviest Riffs of the 1960s in the Loud List above.

66 Most Important Moments in Metal History

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