Christoph von Dohnányi led the Cleveland Orchestra for 18 years. (Roger Mastroianni | Cleveland Orchestra)Christoph von Dohnányi, a conductor known for his illuminating and intellectual approach to music, died Saturday. His death was announced in a statement by the Cleveland Orchestra, which did not specify a cause. Andrew Porter, praising a Cleveland Orchestra performance of Bruckner ‘s Seventh Symphony in The New Yorker in 1988, wrote: “Mr. Klaus von Dohnányi, Christoph’s older brother, served as mayor of Hamburg from 1981 to 1988.