Like Icarus, pianist Lang Lang may have risen too fast, the burgeoning of his immense physical talent--Barenboim once said he must have an extra finger--outstripping his development as a musician. His ability to satisfy critics seems almost inversely proportional to his ability to excite the public. He can be overly flamboyant, yet his extraordinary technique, enthusiasm, and sincerity keep him engaging. Chamber music could be a healthy challenge, forcing him to listen and rein in his exuberance for the good of the ensemble. Here he joins CSO members Yuan-Qing Yu (violin), Yukiko Ogura (viola), Kenneth Olsen (cello), and Michael Hovnanian (double bass) in performing Schubert's Trout Quintet, a joyful piece that reflects the composer's youthful delight at vacationing in the Austrian countryside. Composed for an amateur cellist, it contains wonderful writing for the cello, which is freed by the presence of the double bass to soar melodically. The concert opens with Mozart's Divertimento in E-flat, a masterpiece for string trio in which the voices of the violin, viola, and cello are interwoven to perfection. Elegant, inventive, and profound, it ranks with his best chamber work. a 3 PM, Orchestra Hall, Symphony Center, 220 S. Michigan, 312-294-3000 or 800-223-7114, $31-$68.