Hugh Wolff, the National Symphony's soon-to-depart associate conductor, opened its Beethoven festival at Wolf Trap last night with a concert so fine that it made you wonder why they're letting him go to the New Jersey Symphony.

The real proof of the 31-year-old Wolff's mettle -- and his potential -- as a conductor has been the tendency that, with him, the greater the challenge, the greater the achievement. This has been particularly true in the works of Beethoven -- a circumstance that is not exactly insulting to the reputation of a young conductor.

Last summer this proclivity resulted in an especially memorable Beethoven Ninth at Wolf Trap. Only the slow movement was less than superb -- and that's saying something. Last night that other greatest symphony of Beethoven, the "Eroica," was done even better. Nothing was weak about it. He had the whole epic shape of this work -- a symphony so revolutionary that it inalterably changed the course of music -- fully in hand, its momentum, the staggering intensity of the "marcia funebre" (this was, quite properly, the movement that was played on the field the morning after the slaughter of the Israeli athletes at the Munich Olympics -- a sort of Olympus of tragedy in music).

But if the whole conception by Wolff was grand, particular moments especially linger in the mind: the final bars of the funeral march (their ambivalence just about as well molded as one could ask); the brisk, decisive opening of the last movement; the breadth of that movement's great slow variation in the oboe.

When there is this degree of emotional involvement, the orchestra plays as well for Wolff as it does for anybody. In recent years, only Tennstedt has gotten grander Beethoven -- at least in his heroic mode -- from the players. Wolff has certain musical qualities that make for outstanding Beethoven: a decisive beat, precise attacks and releases, an intuitive and sure rhythmic sense.

He also showed considerable tenderness in the Fourth Piano Concerto, which was played with warmth, if not spectacular rigor, by Bella Davidovich. She certainly draws lovely sounds from the piano, though.

There was also the "Consecration of the House Overture," an underrated masterpiece, played with full tone and precise articulation -- and conducted with authority.