Lyrical duettists Speach (piano) and Schanzer (guitar) are both composers as well as improvisers, and the questions their music prompts are like Chinese boxes. How much of their playing is interpretation and how much is improvisation? How much of their improvising follows fixed structures, and what are those structures? How free are their rules of interpretation? They tend to sound rather like an updated, freely improvising extension of jazz piano great Lennie Tristano and his guitar partner Billy Bauer, without Tristano's odd intensity--though much of their work, such as the intriguing "Blue," is, as one critic noted, to the jazz tradition what Stravinsky's Ragtime is to ragtime. Their background is classical; Schanzer and Speach studied under Morton Feldman, an early investigator of indeterminacy and an ancestor of minimalism. The postmodern oppositions in their music--consonance in dissonance, the harmonic movement of Debussy or Messaien, Jim Hall or Derek Bailey--at best sustain tension and movement without nervosity. Though little known in these parts, Speach and Schanzer are very busy on New York's classical music/jazz/free improvisation scene, collaborating with artists from Joseph Jarman to the Arditti String Quartet to poet Thulani Davis. Which goes to show that the innate attractiveness of this pair's music is as relevant to the present age as the violent sound of their highly amplified contemporaries. Saturday, 8 PM, Southend Musicworks, 1313 S. Wabash; 939-2848.