Ravinia in the North Shore suburb of Highland Park is the summer home of the Chicago Symphony, although every year the pop side of the Festival seems to encroach a little more on the serious. I wonder if Music Director James Conlon had anything to do with engaging Tom Jones and the Squirrel Nut Zippers. Luckily there are two venues at Ravinia, the large Pavilion programmed for the masses, and the 850 seat Martin Theater, where chamber music and song recitals are performed. Bryn Terfel made his American recital debut in the Martin, and it was a coup this year for Ravinia to secure for the theater Matthias Goerne and Christoph Eschenbach’s traversal of the three major song cycles of Schubert in a single week, concerts otherwise heard only in London and Austria. The two artists also gave a public master class coaching Schubert with young singers in the Festival’s Steans Institute training program. It was then a week of sheer delight for lovers of German Lieder, whose average age, sad to report, seemed to hover somewhere around 67.