A church with top-notch musicians among its parishioners is blessed indeed. Pianist Deborah Sobol, a founder of the Chicago Chamber Musicians, has been attending services at Saint James Cathedral for years, and this summer she started a free early-evening recital series called "Rush Hour" there and corralled many of her colleagues to take part. The impressive list of guest performers includes Chicago Symphony Orchestra flutist Mathieu Dufour and clarinetist Larry Combs, and the 45-minute programs range far afield from the usual chamber-music chestnuts: quartets by Faure and Dvorak as well as John Harbison's rarity Book of Hours and Seasons have been performed so far. On Tuesday Sobol will pair up with CSO violinist Yuan-Qing Yu in Mozart's Sonata for Violin and Piano K. 454, a collaboration that promises to make for a special occasion. The sonata demands camaraderie, not just virtuosity, and Yu and Sobol have it--a willingness to blend personalities that they've perfected through decades of playing chamber music. Yu, a prodigy in her native China, came to the U.S. in the 1980s and quickly rose through the ranks to her current position as the CSO's assistant concertmaster. She clearly loves chamber performances, as evidenced by the large number she gives every year; ditto Sobol, who's one of the most sought-after accompanists around. Tuesday, September 2, 5:45 PM, Saint James Cathedral, 65 E. Huron; 312-787-7360.