The British group Deep Purple was one of the earliest hard rock bands. The group’s earliest incarnation—keyboardist John Lord, guitarist Ritchie Blackmore, drummer Ian Paice, singer Rod Evans, and bassist Nick Simper—had a single hit, a cover of an American pop tune called "Hush ♫." The group had little success until 1970, when Evans and Simper were replaced with singer Ian Gillan and bassist Roger Glover. This version of the group released three hit albums in a row: Deep Purple in Rock (1970), Fireball (1971), and Machine Head (1971). Machine Head includes the singles "Smoke on the Water ♫" and "Highway Star ♫," both of which are were major hits. "Smoke on the Water ♫" has the riff-based structure that was a hallmark of the hard rock style.

An early American hard rock band was Steppenwolf, who changed their name from Sparrow to the title of a novel by Hermann Hesse. Steppenwolf’s music was riff-based, although they did not always play the riff throughout the entire song as later hard rock bands would. Their high volume and heavy distortion were important parts of the hard rock genre that had been carried over from psychedelic rock. The band’s hardness was indelibly linked with the 1969 film Easy Rider, which included the songs "Born to be Wild ♫" and "The Pusher ♫" in its soundtrack.