Bassist and composer Jason Ajemian is one of the most mercurial players on the local improvised-music scene, given to taking wild creative leaps without worrying much about whether he can make it to the other side. In part because he’s so hard to pin down, he hasn’t earned the reputation he deserves–despite being a pillar of free-jazz combos like Triage, Mandarin Movie, and Dragons 1976, playing with folk weirdo Josephine Foster in Born Heller, and most recently joining the Chicago Underground Trio. Last fall he debuted a killer band called Day Dream Full Lifestyles, which played pieces he’d structured around the rhythms of breathing, but Who Cares How Long You Sink might be his most peculiar project. A large band with a fluid cast, it’s been slowly morphing for about five years and now makes music that suggests the implacable processes of the natural world, like the motions of tides and glaciers–harmonically ambiguous sheets of sound coast and collide, rippling with texture and erupting with terse melodic fragments. The group’s most recent recording, Folk Forms Evaporate Big Sky (Sundmagi), credits 31 musicians, who gather in soft-focus clusters of brass, reeds, and strings. Their gorgeous renditions of Ajemian’s minimal themes would be hypnotizing if not for his disquieting vocal interjections–he sings in an old-timey wail that sounds like Jandek imitating an Appalachian hillbilly. At press time Ajemian had 14 recruits for this gig and expected to find more; Brad Loving, one of his bandmates in Lobisomem, will screen video during the performance. a 10 PM, Heaven Gallery, 1550 N. Milwaukee (second floor), 773-342-4597, $10 suggested donation. A