Countless classical virtuosos have proven that all the technical brilliance in the world doesn't guarantee the ability to improvise. Chicago-born cellist Frances-Marie Uitti is one of the few musicians who can walk both walks. Now based in Amsterdam, she's highly sought after in contemporary music circles, and prominent composers like Luigi Nono, Giacinto Scelsi, and Louis Andriessen have all dedicated original works to her. She's pushed cello technique forward by developing a twin bowing approach that allows her to play multiple sustained chords, but she downplays her wizardry on her latest recording, There Is Still Time (ECM). The album's a collaboration with writer Paul Griffiths, who composed a series of spoken-word pieces using only the 482-word vocabulary of Ophelia in Hamlet; Uitti creates gentle, brooding lines and textures to mesh with his dramatic readings. More germane to this performance is Sonomondo (Cryptogramophone, 2000), a series of improvised duets with jazz bassist Mark Dresser, who's shown a rare affinity for contemporary classical music. He's expanded his sound in various ways, like developing a set of customized pickups that, placed on different parts of his instrument, better convey his rich tone and rhythmic subtlety. But what comes through on Sonomondo is the sheer variety of sounds--dense, burred, sleek, burnished, and exacting--and the constant dance between the two players. They'll be joined here by Chicago sound artist Lou Mallozzi. On the Punctual Trio's recent Grammar (Rossbin), Mallozzi insinuates himself between cellist Fred Lonberg-Holm and violinist Carlos Zingaro like a gleeful prankster: using samples on turntables and computer, as well as feedback and oscillation, he exemplifies careful listening, darting in and out through even the knottiest openings. Sat 10/15, 8 PM, Renaissance Society, University of Chicago, 5811 S. Ellis, 773-702-8670. Free. All ages.