Master of Reality is the third studio album by Black Sabbath, released in August 1971 . It is regarded by some critics as the foundation of doom metal, stoner rock, and sludge metal. Produced by Rodger Bain, who also produced the band's prior two albums, Master of Reality was recorded at Island Studios in London from February to April 1971. Guitarist Tony Iommi and bassist Geezer Butler downtuned their instruments during the production, achieving what Iommi called a "bigger, heavier sound".
