Sascha Groschang brought out deep, rich tones from her cello as Kairy Koshoeva sent her fingers rippling over the ivory keys during the first fall Downtown Noon Concert. Ms. Groschang, a Missouri Western State University faculty member who has played Carnegie Hall and the Lincoln Center, performed a J.S. Bach solo. Then the two musicians tackled Rachmaninoff, a subject dear to Ms. Koshoeva. She’s the 2004 Gold Medal winner of the Rachmaninoff award given in Moscow. The 40-minute free concert had attendees on their feet responding with an ovation for the duo’s performance. The next free musical event of the series begins at 12:10 p.m. Oct. 2 with a French horn and piano concert.