Om is the post-Sleep project of bassist Al Cisneros and drummer Chris Haikus, the erstwhile rhythm section for that seminal band. Following the 1993 "Dopesmoker" debacle -- in which newly signed Sleep entered into a protracted battle of wills with London Records over the band's refusal to accept that their major-label debut would be anything less than a single 60-plus-minute track about weed -- Sleep fell apart and a disillusioned Cisneros retreated from the music scene for years. In 2004 he and Haikus started jamming again, with the results evolving into Om. San Francisco psych label Holy Mountain released their first collection of material, Variations on a Theme, in 2005. Conference of Birds followed in 2006, and in 2007 Om switched to Southern Lord for their next album, Pilgrimage. Hallmarks of Om's music are deliberately evolving doom metal bass and drum patterns stretched out over long periods, with the changes coming so gradually as to be almost imperceptible. Not surprisingly, the band plays at an absolutely unholy volume live.