Derek Bailey, the pioneering British guitar improviser, has often frowned on repeat matchups of musicians. The idea goes, once you discover the basic MO of another musician, there are no surprises left to cajole the music into unexpected directions. Sweden’s Gush doesn’t necessarily topple Bailey’s idea, but it provides a hearty challenge. Pianist Sten Sandell, percussionist Raymond Strid, and reedist Mats Gustafsson have been performing as Gush since the late 80s, but each brings such a bounty of ideas and techniques that they seem to collectively possess dozens of distinct personalities, daring themselves to discover new terrain with each performance. Gustafsson may be familiar to Chicagoans through the several visits he’s made on his own in the last few years. A highly inventive saxophonist–he created such mutant instruments as the fluteophone, an alto sax mouthpiece crammed into a flute–Gustafsson is a master of extended technique, and his interactive abilities have yielded amazing performances with a variety of local collaborators; in a way, he serves as paradigm for the trio. Whether dueting with knotty percussionist Michael Zerang or working in a trio with bass clarinetist Gene Coleman and guitarist Jim O’Rourke–both of these settings are represented on the excellent Parrot Fish Eye (Okka Disk)–Gustafsson shows resiliency and range. Sandell, on his own Frames (Baunta), goes from a lovely rendition of Monk’s “Coming on the Hudson” to an impressive stab at polyphonic throat singing to dizzying, cluster-laden piano runs. Gush’s From Things to Sounds . . . (Dragon) reveals the group’s depth–exploring everything from explosive bouts of pure energy to gentle, almost microscopic interactions. On a forthcoming collaboration with the violinist Phil Wachsmann the trio brilliantly retools to fit its idiosyncratic recording mate, delivering liquid, loopy gobs of delirious sound. This is Gush’s Chicago debut. Wednesday, 9 PM, Empty Bottle, 1035 N. Western; 276-3600. PETER MARGASAK