What is the secret of the Boston Symphony Orchestra's wondrous playing these days? Can it be seniority? The fact that the orchestra is celebrating its 100th birthday? Hardly, since none of the players was around a century ago.

No, the reason must reside, as always, in the combination of superb musicians and a truly distinguished conductor. Last night in the Kennedy Center he was Sir David Colin Davis.

When Sir Colin conducts Berlioz -- and he has performed almost everything for orchestra that Berlioz wrote -- the result is a high degree of excitment based on authoritative insights. The overture "Les francs-juges" is a dramatic affair built on seemingly slight materials that grows into a structure of imposing proportions, decorated with brilliant coruscations of sound. The Boston brass were more than ordinarily impressive.

At the opposite end of the dynamic and textural scale, Ravel's Rapsodie Espangnole was all seduction, with muted strings sighing and exquisite woodwind solos. David held the orchestra in the palm of his hand to achieve subtle rhythmic and sonorous wonders.

For a finale there was the Second Symphony of Brahms. As it proceeded it sounded as if it had been written for the Bostonians: ideally balanced choirs, and conducting that enlivened while remembering to relax at the right times. At the last, the coda with trumpets blazing was a reminder of all the beauty that had preceded it. It was one of the season's most rewarding concerts.