Black Sabbath were an English rock band formed in Birmingham in 1968 by guitarist Tony Iommi, drummer Bill Ward, bassist Geezer Butler, and vocalist Ozzy Osbourne. They are often cited as pioneers of heavy metal music. The band helped define the genre with their first three albums Black Sabbath, Paranoid, and Master of Reality. Following Osbourne's departure in 1979, the band underwent multiple line-up changes, with Iommi being the only constant member throughout its history.
After previous iterations of the group - the Polka Tulk Blues Band, and Earth - the band settled on the name Black Sabbath in 1969. They distinguished themselves through occult themes with horror-inspired lyrics and down-tuned guitars. Signing to Philips Records in November 1969, they released their first single, a cover of the Crow song "Evil Woman", in January 1970, and their debut album, Black Sabbath, was released the following month. Though it received a negative critical response, the album was a commercial success, leading to a follow-up record, Paranoid, later that year. The band's popularity grew, and by 1973's Sabbath Bloody Sabbath, critics were starting to respond favourably.