"This is better than the soaps," quipped Rene'e Channey last night on the Capitol lawn, as her co-host Dennis Owens ran through the scenario of Berlioz's "Symphonie Fantastique," a lurid tale of blighted love, attempted suicide and narcotic-tinged fantasies of murder, the guillotine and satanic rituals. As a matter of fact, the National Symphony's Labor Day concert was very much like a soap opera, lacking in subtlety but with lots of vivid incidents outlined in bold, primary colors.

It began with the "Academic Festival" Overture of Brahms, described by the commentators as a medley of old German drinking songs and accepted more or less in that spirit. The audience was invited to sing along in "Gaudeamus Igitur," but if anyone did, the voices were lost in the vast, open spaces.

In the Berlioz, the orchestra had some unplanned accompaniment from planes passing by, notably at the beginning of the "March to the Scaffold," where the noise seemed quite appropriate, and at the end of the slow movement, where the hint of an approaching storm, usually entrusted to the percussion, was reinforced by rumbles overhead.

Despite such assistance -- or perhaps partly because of it -- the interpretations of guest conductor Roger Nierenberg seemed competent (for an outdoor concert with short rehearsal time) but not specially distinguished. Tempos were generally well-chosen if not particularly flexible, and the sound had clarity and decent balance as sampled from several parts of the listening area. The last two movements of the Berlioz created a satisfying tumult, and the tunes in the Brahms emerged with exemplary clarity. Perhaps it is unrealistic to ask for more in the circumstances. Certainly the large and enthusiastic audience was satisfied; it indicated so with applause after each movement of the Berlioz.

There was special interest in the central item on the program, the First Violin Concerto of Max Bruch, because it introduced the NSO's new concertmaster, William Steck, as soloist. He opened with warm tone, plenty of vibrato and slow, luscious phrasing that bodes well for the "Scheherazade" solos he will be performing in a few weeks. This kind of playing is what Bruch mostly demands until the last movement's high-speed acrobatics, in which Steck showed suitable dexterity. His E string sounded slightly shrill once or twice, but that may have been the fault of the sound system.

The music did not probe Steck's dramatic powers, as the concertos of Brahms or Sibelius would, but he gave what Bruch demanded, expertly and with polish. If he lacks the special magnetism of an internationally renowned virtuoso, that is, after all, not what one seeks in an orchestra's concertmaster.