The Dallas Symphony has a new music director. Jaap van Zweden, a 46-year-old Dutch conductor who has been building his reputation on both sides of the Atlantic, will take the helm in the fall of 2008. “It’s no secret that tidying up the DSO’s violins will be a priority, as well as generally tightening an ensemble that too often played on autopilot for former music director Andrew Litton… Above all, Mr. van Zweden must re-energize the orchestra and get the city excited enough to fill conspicuous swaths of empty seats at the Meyerson.”