After cutting three albums that would almost singlehandedly establish the sound of heavy metal for a decade to come and remain the foundation for its sludgier, more stoned variants well into the 21st century, Black Sabbath decided to make a few key trades. So they swapped out recording in London for Los Angeles, sweet leaf for white flake, and a relentless churn of downtuned doom for… a lot more of it, but with a few unprecedented tweaks to the itinerary. The giddy full-rockets-ahead “Supernaut” is their most danceable(!) cut and features both a ridiculously great quasi-samba breakdown and one of the best lines Ozzy ever belted (“I’ve seen the future and I’ve left it behind”). And the minimalist piano-and-Mellotron balladry of “Changes” remains a remarkable outlier in the band’s catalog, one of the most unguarded moments of heartbreak in the entire hard-rock pantheon. And since they’re still at peak power when it comes to heavy-riffing, percussively bludgeoning rock, they hit the mark with blunt-force power on cuts like the coke-escapist trudge “Snowblind” and the tempo-escalating defiance of closer “Under the Sun / Every Day Comes and Goes.”