It's hard to believe that it's been 43 years since Black Sabbath unleashed the classic 'Paranoid' album on a largely unsuspecting public.

Released on Jan. 7, 1971 in the U.S. -- and four months earlier, Sept. 18, 1970 overseas -- the band's second album would prove to be not only one of the defining moments in their catalog, but also for all of heavy metal. With their self-titled debut album, Black Sabbath had established their unique style, and had begun to build a devoted audience. 'Paranoid' would follow a similar path, but with a more focused energy and greater detail to songwriting, ultimately opening the door to worldwide commercial success.

The album kicks off full force with 'War Pigs', which was the working title of the LP. The doom-laden, riff-heavy track is a powerhouse, not only musically, but lyrically as well, standing as one of the more potent anti-war songs of the era. "You could just see a lot of things going wrong in the world, and nobody was saying anything about it," bassist and lyricist Geezer Butler recalled in the 'Paranoid: Classic Albums' documentary, "Bob Dylan had long since faded from the present memory and there was nobody talking about the stuff I wanted to talk about, political stuff, so that's what inspired me."

The band are noticeably tighter and the songs more focused on the album. The title track is a pure and solid punch of rock and roll. 'Paranoid' is the normally expansive Sabbath sound distilled into a straight ahead three minute song. The simplistic riff at it's core has all the energy of punk rock, with a razor sharp metallic attack. Ozzy Osbourne's vocal attack is spot on and the hard edged production of Rodger Bain still resonates with brutal power all these years later. Gears shift instantly with 'Planet Caravan,' a moody, psychedelic number that rolls along on waves of conga drums, phased vocals and mellow guitars. It is another fine example of Black Sabbath never being the one-trick pony their detractors claimed them to be. "We always liked variation," adds Butler, "I think that's another Beatles influence. We didn't do a 'heavy metal' album from track one to track ten or whatever."

'Iron Man' is up next to round out side one. Tony Iommi's guitar riff belongs on the Mount Everest of massive riffs, right alongside 'Smoke On The Water' or 'Louie Louie.' The tale of overcoming obstacles and seeking revenge in a world gone wrong connected perfectly with the band's fans -- and along with the title track, helped get the band on American radio.

Side two kicks in with the evil glowing stomp of 'Electric Funeral,' which continues the themes of despair and impending apocalypse. Once again, Ozzy's vocal line follows the riff of Iommi's guitar and combines with Butler's bass to create a powerhouse wall of sound. The song breaks off midway for a metallic jazz spiral, before landing firmly back on planet riff.

'Hand Of Doom' is a startling track with yet another jagged riff at its heart, this time out tackling the horrors of drug addiction, in particular, the addiction of soldiers returning from Vietnam as junkies. The interplay of the rhythm section is stellar, and Ozzy delivers one of his finest vocals of the album. 'Rat Salad' is a brief showcase for Bill Ward that sets the table for album closer 'Fairies Wear Boots.' The jazz-driven tempo takes the song into another direction and proves once again that there was more to these guys than just heavy plodding. Iommi, Ward and Butler create a sonic metal swing groove that gets heavier and heavier as it sails along, making it a perfect way to close up the album.

The album was released in January of 1971 in America, and came just shy of the US Top 10, paving the way for the continued accession of the band. It topped the UK charts upon release a few months earlier. "It was such a brilliant time," recalled drummer Bill Ward in an interview with Kerrang. "We were constantly touring. The music was the beginning of a new era. I think it was the crucible of something that was to be way bigger than us."