Everyone needs a vacation, even musicians, and the summer is quite naturally a time that the classical music world slows down. So this is it for your Classical Music Agenda, until August. This week’s installment will be a little longer than normal, because there are several interesting things happening over the next couple months. If you want to hear some music this summer, you can, and here’s where. HEADLINES: >> The most important classical music…

Chinese superstar pianist Lang Lang joins the National Symphony Orchestra in this weekend’s concerts at the Kennedy Center Concert Hall, beginning this evening. He was originally scheduled to give the premiere of a new piano concerto by American composer Jennifer Higdon (b. 1962). However, as announced by the NSO in late March, the composer and the pianist issued a joint statement, saying that “differences in interpretive viewpoints and styles have led us both to feel…