In an elegant and distinguished performance, Gunther Herbig conducted the National Symphony Orchestra Saturday night at Wolf Trap in top-flight presentations of Brahms' Violin Concerto and Dvorak's Symphony No. 8. The fact that Itzhak Perlman took the solo part in the Brahms helps to explain part of the evening's success, but Herbig and the orchestra must take credit for the exceptional symphony.

In spite of intense demands on the soloist's technique and endurance, Brahms' Violin Concerto in D Major, Op. 77, is nevertheless a noble and reflective work. Perlman's striking display was always accompanied by a transparent tone, dignified phrasing and intelligent musicianship, nowhere more evident than in the glorious adagio. Here the lyric outline was offered with purity and consummate styling by violin and oboe.

The deft and cogent handling of Dvorak's Symphony No. 8 in G Major, Op. 88, lent the work genuine authority and an almost regal bearing. The great intermingling of themes was approached solidly but not at the expense of warm sonorities, rhythmic spark and tempting orchestral color. Herbig's conducting was thorough, finely crafted and totally effective.

Wagner's "Siegfried Idyll," scored for chamber orchestra, was completely respectable, but it couldn't keep step with its concert companions. The opening melody might have been projected with more fluidity, for example, and the strings could have stood sharper intonation in spots. Yet, with two other hefty works splendidly played, there can be no real complaints.