After nine years, Christoph Eschenbach leaves as music director of the Ravinia Festival this week. “If James Levine kicked Ravinia’s international profile up several notches, Eschenbach certified it as a full-service festival – a place where young musicians and seasoned artists can strike sparks off one another, where top-level chamber music thrives, where amazing things can appear out of nowhere like the fireflies that dance among the picnickers on the lawn. He has set the spontaneous tone for a summer place where performers unwind in postlude concerts that have been known to go on well past midnight.”