Mozart, who was an exceptionally gifted violinist as well as a great pianist, wrote all five of his violin concerti before he was 20. In the first two the orchestra is primarily an accompanist, but in the third the orchestra and soloist become true partners. The first movement of the third is sprightly and playful, the second movement has a wonderfully languid adagio that Mozart made ethereal by replacing the oboes with flutes, and the third's cheerful rondo includes a marvelous slow dance. Making her Chicago debut as the soloist will be Isabelle van Keulen, who was born in the Netherlands in 1966 and studied at the Salzburg Mozarteum. She's appeared with orchestras throughout Europe, including the Berlin and London philharmonics, and is the founder and artistic director of the Delft Chamber Music Festival, where she's performed with, among others, Gidon Kremer and Leif Ove Andsnes. Also on the program are Howard Hanson's Merry Mount Suite and Richard Strauss's lush, brilliantly orchestrated tone poem An Alpine Symphony, a large-scale, highly descriptive work about a mountain climb that begins and ends with a mysterious evocation of night. Carlos Kalmar conducts. Sat 7/1, 9:30 PM, Pritzker Pavilion, Millennium Park, 100 N. Michigan, 312-742-7638. Free.