LENOX - When the Boston Symphony Orchestra is in the zone, it is serious fun. On paper, Sunday’s Tanglewood program seemed meat-and-potatoes classical: Beethoven, Bruch, Dvorák. But in practice, it also called to mind the BSO’s earliest seasons, their late-19th-century salad days as a new-music group specializing in the latest modern German school; and the orchestra nicely recaptured that evangelizing mojo, polishing up the old silver to a fresh shine.
Guest conductor Herbert Blomstedt had also led Friday’s performances, which were lovely but not terribly urgent. On Sunday, that haze was dispelled from the get-go with a tight account of Beethoven’s “Egmont’’ Overture, a stringent, streamlined narrative of struggle and triumph. (It almost plays like the Fifth Symphony’s highlight reel.) The playing was spot-on; the dramatic intensity unflagging.