White it’s roots have been around for years, heavy metal as we know it has existed for 46 years now. It was ushered in on February 15th, 1970 with the release of Black Sabbath’s self-titled LP. And while many bands take years (or if you’re Tool, decades) to release follow-up albums, on this day in 1971, Black Sabbath released their third album in a year and a half, the classic Masters of Reality. Kicking off with a cough from Tony Iommi that was captured after Ozzy Obsourne handed him a joint, “Sweet Leaf” ushers in what was the  band’s heaviest album to date, and still one of it’s most popular. It was recorded during two sessions in London during February and April of 1971, and debuted stateside at #8, their highest-charting album until 2013’s 13 became their only chart-topping album.

One of the reasons Masters of Reality is so heavy is that Tony Iommi and Geezer Butler played with instruments that were tuned down. While it’s sonically something that was new at the time, the primary reason was that it was easier for Iommi, who had the tips of two of his fingers cut off in a factory accident, to play. So if you’re wondering why “Into the Void”, “Children of the Grave” and “Lord of This World” sound so massive even a middle-aged adult later, that’s why. And while the band’s title track from their first album the previous year might have invented doom metal, the aforementioned downtuned songs, as well as “Sweet Leaf,” were where stoner metal began. It’s amazing that what’s essentially a six-track album (there are two instrumentals that make up two minutes of the album), had the staying power that it has to this day, and that four of its songs are still set list staples.