Breaking up was the best thing Sleep ever did. Sure, they made Jerusalem, a stoner metal masterpiece that was basically an hour of Black Sabbath's "Iron Man" riff. But the record was a logical limit-- how much more droning and Sabbath-esque could a band get? When the band split up in the late 1990s, it birthed two behemoths: Guitarist Matt Pike formed High on Fire, while bassist Al Cisneros and drummer Chris Hakius formed Om. High on Fire's mixture of Motörhead and Black Sabbath has found considerable success, and Om's drums-bass-vocals shtick has also garnered a large following. The two bands are as if Sleep separated into its constituent elements: High on Fire continue (and accelerate) Sleep's midrange roar, while Om explore Sleep's mantra-like low end.