The danger of the name Boulder Acoustic Society is that, taken literally, it could be misleading. Its associations ring official. Is this a political party? An after-school club? A gray-bearded bluegrass night turned Masonic? The fact is that the Boulder Acoustic Society is one of the most youthful and adventurous string bands working on the Colorado folk and bluegrass circuits. While their name implies tradition, the four-piece pushes roots music until it nearly crumbles, all the while clutching instruments straight from grandpa's attic: Aaron Keim plays string bass and ukulele. Kailin Yong rips a mean violin. Scott McCormick pushes a squeezebox, and drummer Scott Aller plays junkyard percussion--old faves like the washboard, mixed with makeshift oddities like a wooden box and sea shells. Their aesthetic runs a wide genre gamut that blends barroom blues, old American folk and bluegrass balladeering, arena-rock irony, Dixieland jazz, punk intensity, Elvis-lipped rockabilly, world music, and vague, yet omnipresent, Vaudevillian vibes. Like many a modern mash-up, Boulder Acoustic Society's polyamorous musical appetite doesn't succeed because of its outlandishness. It has to prove itself beyond the exhausting this-style-meets-this-style PR blurbage.  The Tao of B.A.S. works primarily because they are damn good technical musicians: The Singapore-born Yong is classically trained. McCormick is into modern jazz piano, and Keim is such a wiz at dusty instruments like rarified ukulele banjos that he makes them himself. B.A.S. also tour extensively, and long van rides and countless shows have both tightened up the band's sound and road-tested their experimental tendencies. Judging by their latest LP, The Caged Bird, the road has emboldened them to try anything. And that's exciting. It's fun to watch energy and inspiration come out of what should really sound like a train wreck. Brooklyn-based retro-youngins The Wiyos are headlining the show, so be sure you're seated in time to support the locals. 8 p.m. Swallow Hill (Daniel's Hall), 71 East Yale Ave., Denver. $12-15. 303-777-1003