Last night began week five of this summer’s Fort Reno concerts. The annual series of musical triptychs, which take place in an improvised venue in the Tenleytown park, may be the most urbane happening of any place in DC. Amid the mild yellow-orange light of a summer evening, a small local band plays and a few hundred people of various ages watch while they sit on the grass. But beyond that and behind the stage, those less interested in the concert partake in all kinds of leisurely activity. Really, I’ve never seen the park so well used.