Longtime Wilco fans have occasionally gotten frustrated with leader Jeff Tweedy when he's pushed the group into avant-garde territory. But by the adventurous standards of Glenn Kotche, who landed in Wilco's drum chair during the Yankee Hotel Foxtrot period, Tweedy's a piker. Kotche, who's joined at the Larimer Lounge by Porlolo and Bela Karoli (formerly Bluebook), kicks off 2006's Mobile, his Nonesuch Records debut, with "Clapping Music Variations," an adaptation of a piece by minimalist composer Steve Reich played mostly on marimba, and things only get edgier from there; among the other offerings is "Fantasy on a Shona Theme," in which a melody inspired by African Mbira music is transposed for vibraphone. These instrumental explorations touch upon jazz, classical and assorted folk styles without being in thrall to anything other than Kotche's restless intellect. Granted, some listeners may find the material to be inaccessible at first -- but the extra effort to appreciate his virtuosity is apt to pay off for most people, just as it does when Tweedy takes a tangent. And that's not frustrating at all.