Although his first instrument was actually the piano, Ralph Towner's guitar work in the 1970s proved to be the last word for a broad array of listeners. With the Paul Winter Consort and later with its offshoot, the quartet Oregon, Towner wove folk and classical music into his compositions and improvisations, tying them all together with a pianistic technique; the results included some of the most affecting and exquisite music of the last decade. A clear and cool blend of artist and craftsman, Towner is so unruffled by his own virtuosity that you can watch him and assume that's just the way the instrument is played--until you hear someone else give it a whirl. It's been several years since Chicago has gotten to hear Towner's guitar constructions, glittering with rococo lacework but sturdy underneath, and then only within the context of the quartet. His much copied style remains individualistic even as it grows more familiar; the chance to hear the original, and in such cozy surroundings, should sound a siren's song for music lovers of every stripe. Sunday, Club Lower Links, 954 W. Newport; 248-9496.