The Concertgebouw Orchestra did not unleash its full greatness until last night in the fourth and final work of its two programs here--the first pre-20th-century classic it played on this visit -- Berlioz's "Symphonie Fantastique." The three works that had gone before -- Mahler's Seventh Symphony on Sunday night, Ravel's "Valses Nobles et Sentimentales" and the "Movements" of contemporary Dutch composer Tristan Keuris last night--had been variously impressive, but they turned pale in the reflected glory of the Berlioz, the first showpiece composed for a virtuoso modern orchestra and still one of the best.

The principal beneficiary was the string section. Compared with the eloquent but rather prolix Mahler, the Berlioz is a holiday for strings in its first three movements and uses them for some impressive fragmentary comments and special effects in the concluding "March to the Scaffold" and "Witches' Sabbath," which are primarily the playground for winds and percussion. Almost from the beginning, when the violins made their first subtle diminuendo and the lower strings came in with a rich pizzicato, there was a glow in the string tone, a subtlety of phrasing and dynamics, a superbly poised balance that had not been heard before--although there had been many impressive moments in the other works. Clearly, Bernard Haitink's interpretation of this symphony is more matured, more refined than any of the others he chose to play in Washington.

Not that the others were bad or badly done, but the Berlioz was in quite another class, as a composition and most emphatically as a showpiece. It is a work with an impressive performance tradition, associated with most of the world's great orchestras and conductors, and its performance made comparisons easy and inevitable. From such comparisons, last night, the Concertgebouw emerges as one of the world's three or four great orchestras, and perhaps The Netherlands' most significant contribution since Rembrandt and Vermeer to the world's enjoyment of the arts. It is an international treasure and its visit is a most appropriate way to celebrate 200 years of unbroken friendship between our two countries -- a gesture to make any American music lover rejoice in that friendship.

The relationship, in its cultural dimensions, is obviously important to our Dutch friends. The visit of the Concertgebouw is only part of a massive and multifaceted cultural exchange, which includes many other programs in music and the visual arts--notably a season-long residence of the extraordinary violinist Jaap Schro der with the Smithsonian's musical ensembles. During intermission last night, hundreds of audience members visited a mobile booth that had been set up on the outdoor promenade outside the Concert Hall, where videotaped performances of Dutch music were being shown and displays were extolling the music of Netherlands composers from the 15th century (Josquin des Prez and Heinrich Isaac) to the present. One of the contemporary works on display was the Keuris Movements, whose score could be browsed while its sonic impact was still fresh in the ears.

In either form, it is an exercise for a virtuoso orchestra, built of very succinct phrases in four movements that echo the pace and moods if not the forms of the classical symphony. A first hearing left me impressed with the composer's knowledge of orchestral resources and his spartan economy of form but wishing that he had allowed the music to expand into lyricism more often. It did give the orchestra's various sections and first chairs some fine opportunities to show their ability, but it suffered (as most music would have suffered) by comparison with the Berlioz.