The classical music season got officially under way this weekend, and there will be more and more choices facing eager listeners. Even if you cannot afford all the concerts you want to attend, since local radio station WETA, at 90.9 FM, went back to a classical format, there is more local music on the airwaves, too. Tune in this evening (September 16, 7 p.m.) to the live broadcast of the National Symphony Orchestra’s Season Opening…