Typically, we don't care much for cover bands, especially Zeppelin cover bands. But here we'll make an exception, because "Stairway to Heaven" in the hands of a 50-piece orchestra is a far cry from the twaddlings of a couple middle-aged Robert Plant wannabes. The two-hour production, which comes complete with arena-caliber lighting design, augments 18 faithfully reproduced Zeppelin classics with an orchestral wash of color and sound. While this kind of thing could easily become cheesy, conductor/arranger Brent Havens, who originally conceived the piece for the Virginia Symphony, keeps the focus on the music.