Illinois’s Ravinia Festival is celebrating its 100th birthday this summer, and organizers have created a season designed to call everyone’s attention to that fact. “The nation’s oldest music festival will surround the resident Chicago Symphony Orchestra with programs and activities — 100 nights in all — that look back to Ravinia’s origins in 1904 as a ‘high-class amusement park,’ its early reign as the summer opera capital of the world, and its subsequent history as a major international center of music, dance and theater.”