The compositions bassist Mark Helias brings to his latest album, Verbs of Will (Radio Legs, 2003), sound deceptively simple; from the warm, low-down blues of "How 'Bout It" to "Give Up the Ghost," an appealing blend of fatback heft and west-coast cool, his melodies are never convoluted or busy. That's plainly by careful design. Apparently taking the group's name as a credo, Helias has constructed his minimalist material to withstand far-flung interpretation by himself and his collaborators, tenor saxophonist Tony Malaby and drummer Tom Rainey. Repetitive riffs like the one at the core of "AKA" are passed from hand to hand: Helias holds it down for a rangy, striated solo by Malaby, who then cycles through the same pattern so Helias can let his bow fly. Most often Helias creates an armature with his deep, woody lines, allowing Malaby and Rainey to twine tangled harmonies and fractured rhythms around him only to rearrange things tidily as each piece winds down. Rainey, in particular, is a master at splintering grooves into jagged scraps while always keeping some semblance of pulse alive. But all three players are in perpetual motion, constantly changing places; Open Loose is like a tightrope act where the performers take turns holding the net. Wednesday 29, 9:30 PM, Empty Bottle, 1035 N. Western, 773-276-3600 or 800-594-8499, $10.