Black Sabbath were an English rock band, formed in Birmingham in 1968, by guitarist and main songwriter Tony Iommi, bassist and main lyricist Geezer Butler, drummer Bill Ward and singer Ozzy Osbourne. Black Sabbath are often cited as pioneers of heavy metal music. The band helped define the genre with releases such as Black Sabbath (1970), Paranoid (1970) and Master of Reality (1971). The band had multiple line-up changes, with Iommi being the only constant member throughout its history. On 7 March 2017, Black Sabbath announced they had disbanded.