A dazzling exponent of extended technique, Dutch improviser Luc Houtkamp provides an exhilarating exploration of sounds and how to make them. The Songlines, a definitive 1991 solo saxophone recording, highlights many of his favored tacks, including adventurous, often breathtaking overblowing and circular breathing. The album's title piece dissects a lengthy upper-register squeal with sour decay, compact sound knots, and jags of powerful silence. Many solo sax improv performances stress spontaneity, but Houtkamp is more interested in pushing toward the margin. Focusing on one or two techniques with microscopic clarity, he burrows into a minute world of sound, reveling in its textures, attacks, and dynamics. He's not for everyone, but anyone interested in improvisation as a vehicle for investigating subtle shades of sound shouldn't miss this sonic scientist, who pulls it off with a minimum of academic dryness. Saturday, midnight, Lunar Cabaret & Full Moon Cafe, 2827 N. Lincoln; 327-6666.