The concertmaster has some largely symbolic duties, like playing a tuning A for the orchestra before each performance, but as head of the violins he also does more than any other musician to shape the ensemble’s sound–the whole section follows his bowing, and no one else is spotlighted in solo passages so often. The Chicago Symphony Orchestra has been fortunate to employ Samuel Magad as concertmaster since the 70s, when Georg Solti put the CSO on the world map; for a number of years, however, the sturdy Magad has been sharing his post with a series of other principals, each a potential successor. Robert Chen has held that position since last year, and if he ends up taking over for Magad his lovely, fluent, and understated playing promises to further invigorate the CSO’s strings. (The violins and violas have already improved remarkably with the influx of new blood that brought Chen on board.) Chen, a native of Taipei, earned a master’s from Juilliard in 1991, and though he’s been a guest soloist on the international circuit and performed recitals with the likes of Emanuel Ax and Richard Goode, he seems to have forgone star status for the security and rootedness of life with an orchestra. This Sunday at Ravinia, he’ll be a featured soloist in Saint-Saens’s clever and urbane La muse et le poete, opposite the evening’s headliner, cellist Yo-Yo Ma. Ma will also play Elgar’s lyrical Cello Concerto, and the CSO’s reliably superb flute principal, Mathieu Dufour, will be featured in Jolivet’s jazzy Flute Concerto. Rounding out the program is Stravinsky’s suite from The Firebird; Christoph Eschenbach conducts. Sunday, 7 PM, Pavilion, Ravinia Festival, Green Bay and Lake Cook Rds., Highland Park; 847-266-5100. Chen will also participate in an all-Beethoven recital at 9:30 in Ravinia’s Martin Theatre, performing Violin Sonata no. 5 (the Spring Sonata) with Eschenbach on piano; tenor Vinson Cole will sing a group of Italian songs, and Eschenbach will play the Moonlight Sonata. TED SHEN