Saxophonist Urs Leimgruber--definitely not a household name (not even in my household)--offers two quite different but related approaches to his music. When he plays unaccompanied, he concentrates on repetitive, scientific investigations of the instrument's capabilities: like Roscoe Mitchell, he uses overtones, multiphonics, and an exquisite control over the instrument's most difficult expanses to create entrancing patterns. (Unlike Mitchell, Leimgruber sometimes makes these sound like a sample of Philip Glass.) But with his trio--starring the iconoclastic and much respected drummer Fritz Hauser--Leimgruber takes the results of these investigations and turns them into more fully realized musical experiences in which free-flowing melodies and fluid harmonies are emboldened by his technical wizardry. Relatively few saxophonists, and only a handful of Americans, have chosen his path; critic Peter Ruedi thinks that Leimgruber's "emancipation of the saxophone has to do with an archaic approach to the instrument...making the instrument more elemental." Though he now lives in Paris, Leimgruber was born in Switzerland, and this concert is one of a series of cultural events underwritten by the Swiss government to celebrate the 700th anniversary of the nation's federation. (It's also the first of two nights filled with daring and committed musicianship, since trumpeter Paul Smoker--whose virtuosity constitutes an embarrassment of riches--brings his trio to the same club on Saturday.) Tonight, 8:15, Southend Musicworks, 1313 S. Wabash; 939-2848.