This New York band is among the most accessible avant-prog acts going, and for one simple reason: no matter how far-out their unpredictable song structures, no matter how rich their dissident dissonance, no matter how jittery their pattering vamps or abrupt their metric and textural shifts, they utterly lack the diddlier-than-thou machismo that makes so many similar bands seem outright hostile to their audiences. The new Arms (Planaria) is Zs’ first studio full-length in more than three years, but they’ve certainly kept busy–last year they released a three-inch CD and a live album and contributed to a Tzadik disc compiling interpretations of Earle Brown’s works, and the other projects involving members of the collective are too numerous to list here. The music on the new record creates a constant sense of tingling anticipation that borders on anxiety, but there’s real warmth in it too–though admittedly it seems to come from an unfamiliar source, not necessarily our trusty old sun. The group has gone through a few lineup changes since it formed in 2000: for this tour Zs are a quartet with a drummer, a saxophonist, and two guitarists (one of whom doubles on electronics). KK Rampage and Wizie open. a 9:30 PM, Empty Bottle, 1035 N. Western, 773-276-3600 or 866-468-3401, $7.