Bassist-vocalist Al Cisneros and drummer Chris Hakius, once two-thirds of the mighty Sleep and now both halves of the duo OM, named their latest album, Conference of the Birds (Holy Mountain), after a 13th-century Persian Sufi epic whose title is more often translated as “The Parliament of the Birds.” To my ears “conference” has a sort of fluorescent-lit office-bound quality to it, but there’s nothing else mundane about the album: Cisneros and Hakius may not have the maniac energy of Sleep guitarist Matt Pike, who now fronts High on Fire, but their long-haul focus produces its own kind of catharsis. Om’s 2005 debut, Variations on a Theme, was three sprawling tracks of cyclical, hypnotizing grind, tight but sludgy, with Cisneros delivering his philosophical-psychedelic lyrics with the same chilling, tranced-out affectlessness Ozzy Osbourne managed at his most doped-up and visionary. The two tracks on Conference of the Birds, each more than 15 minutes long, build on this pretty damn fundamental fundament by stretching toward a firmament. Both words and music seem to be trying to paint an outer landscape, not just an inner one–a battle in the desert, an imam calling from a mountain, an opium den on Planet Heavy–and the whole thing’s more open, fluid, and expansive. –Monica Kendrick

PAUL FLAHERTY improvises his music completely in the moment, but that’s not to say there’s no history in it. His woolly sound, honed in decades of wee-hours sessions on the streets of his native Hartford, Connecticut, owes an obvious debt to the old-school energy music of the late 60s: like Albert Ayler and Peter Brotzmann, the 57-year-old alto and tenor saxophonist plays overblown, rippling lines with enough force to ventilate your best Kevlar vest. On his recent solo CD, Whirl of Nothingness (Family Vineyard), he punctuates coarse, furious flurries with brief interludes of tender lyricism, which only serve to intensify the impact of the mayhem around them. Flaherty’s fond of drums-and-sax duos and has sustained a long, well-documented relationship with Randall Colbourne; more recently he’s been recording and touring with Chris Corsano, who accompanied him at his Chicago debut two years ago. For his second trip to town Flaherty will work with local drummer FRANK ROSALY, whose dynamic and energetic playing with the Rempis Percussion Quartet suggests he’s got the chops to match the saxophonist’s ideas and the stamina to keep up with him. –Bill Meyer

Om headlines; Subtle, the Punks, and the Flaherty-Rosaly duo open. This show is part of Adventures in Modern Music; see page TK for a complete festival schedule. a 9 PM, Empty Bottle, 1035 N. Western, 773-276-3600 or 866-468-3401, $15.