Black Sabbath is credited with creating heavy metal. The success of their first two albums - Black Sabbath and Paranoid - marked a paradigm shift in the world of rock. Not until Black Sabbath upended the music scene did the term "heavy metal" enter the popular vocabulary to describe the denser, more thunderous offshoot of rock over which they presided. With their riff-based songs, extreme volume, and dark, demonic subject matter, Black Sabbath embodied key aspects of the heavy-metal aesthetic. Yet in their own words, they saw themselves as a "heavy underground" band. That term denoted both the intensity of their music and the network of fans who found them long before critics and the music industry took notice.

The demanding pace of the road and various lifestyle excesses began catching up with Black Sabbath by the mid-70s following the release of five consecutive genre-defining albums (Black Sabbath, Paranoid, Master of Reality, Vol. 4, Sabbath Bloody Sabbath). Their next three albums - Sabotage (1975), Technical Ecstasy (1976) and Never Say Die! (1978) - all had memorable moments but lacked the unalloyed brilliance of their predecessors.

After a brief break-up following the Technical Ecstasy tour, Black Sabbath and frontman Ozzy Osbourne reconvened for their swan song Never Say Die! Osbourne called the release "A very varied album...it's not just steamhammer headbanging stuff all the way through" and the 9-song set ranges from the potent title track to the synthesizer-heavy "Johnny Blade" to the experimental ballad "Air Dance." The cracks in Black Sabbath's facade became permanent, however, when Osbourne quit for good in 1978, following the checkered Never Say Die! tour.