“They played me the demo, and I told them I thought it was the Kashmir of the ‘90s. The riff was astounding. To my knowledge, they never had anything so heavy, so punchy and powerful. Rhythmically, I could tell it had the potential to be absolutely crushing!

“We were in pre-production, which was uncomfortable because nobody had ever made them go through their songs in such a deliberate way before, and six songs in Sad But True came along. Suddenly, I realized that every song, including this one, was in the key of E.

“I brought this to the band’s attention, and they said, ‘Well, isn’t E the lowest note?’ So I told them that on Motley Crue's Dr Feelgood, which I produced and Metallica loved, the band had tuned down to D. Metallica then tuned down to D, and that’s when the riff really became huge. It was this force that you just couldn’t stop, no matter what.”

Listen: Sad But True