"I have always heard music and riffs internally throughout my life," says Al Cisneros, bassist and vocalist of San Francisco trance/doom duo OM. He and drummer Chris Hakius have been challenging the definitions of "heavy" since their high school band Asbestos Death morphed into stoner icons Sleep in the early '90s. When a major label unceremoniously shelved Sleep's third and final record, guitarist Matt Pike left to start High on Fire. Al and Chris took some time off, ultimately regrouping with a fresh followup to their spiritual metal thread.

Cisneros describes this initial period in the same academic/prophetic language that he employs when writing lyrics: "Stepping away from an orthodox band setup for those interim years provided uninterrupted focus with the internal music, to examine its intensity, to think about life. We didn't really think about the next band, even when it was forming. We just noticed that all the necessary elements were already there: drums, bass, and vocals. The core tools were already present, in addition to the most important fact—us two band members understood each other as friends and as collaborators."

Live and on record, the OM formula is elegant. Simple in that electric bass, crushing drums, and incessant muted vocals are used throughout. Intricate in the braided DNA-like rhythmic structures that constantly change and reflect each other. It's very easy to hear, very difficult to count, always rewarding to experience. Their second album, Conference of the Birds, contains two leviathan tracks. "At Giza" conjures the mood and voicing of Pink Floyd's Saucerful of Secrets with its contemplative chants and psychedelic cymbal wash. The song spends 15 minutes riffing in a Möbius strip, finally yielding a heavy crash and lapsing into an implied eternity thanks to a long, slow fadeout. Track two, "Flight of the Eagle," is more referential to Sleep's final album Jerusalem (or Dopesmoker depending on which version you own), with its massive repetition and crunch.

In the few years that OM has existed, High on Fire has toured around the US and Europe countless times, and truly eclipsed the Sleep legacy. In contrast, OM has recorded two albums with Sleep producer Billy Anderson, and shared vinyl with Six Organs of Admittance and Current 93. But only special event concerts (no tours) have coincided. I asked Cisneros about their relatively few shows with other "doom" bands. He told me that "genre classifications are very divisive things. Sometimes genres take on the mentality of political parties, organized religions... develop a pack-like way of thinking. Life is too short to get caught up in all that."

When I asked him if his ride up to the majors and back down gave him any perspective on whether the music industry is headed in the right direction, his response was as Zen as a fortune cookie: "I don't think it's any better or worse now than before."