Using the jaw-dropping extended technique of Evan Parker as a starting point, fellow British saxophonist John Butcher has done much to advance free improvisation. An agile, diverse musician, Butcher has proved his mettle in a variety of contexts. On Spellings his group Frisque Concordance--with pianist Georg Grawe, drummer Martin Blume, and bassist Hans Schneider--provides a clinic for delicate four-way interplay. Last year's Respiritus found him dueting with extreme vocalist Vanessa Mackness: casting long sinewy lines, they deliriously fucked with pure sound--their swoops, gurgles, and snorts shimmying together with amazing intuition. Yet Butcher's most powerful recording may well be 1992's 13 Friendly Numbers, a collection of both solo and multitracked improvisations. Whether studying something as small as a sax's tongued harmonic pops or cutting slices of more linear and lyrical playing, Butcher is a complete musician. For his Chicago debut he'll perform a solo set, and then a second set with a host of terrific local players--Kevin Drumm, Terri Kapsalis, Fred Lonberg-Holm, John Corbett, Kent Kessler, and Ken Vandermark. Wednesday, 9 PM, Empty Bottle, 1035 N. Western; 276-3600.