Widely known and admired for their television series, "Previn and the Pittsburgh." Andre Previn and the orchestra of that city played a concert last night in the Kennedy Center. It closed in a burst of glory with the First Symphony of William Walton.

It is hard today to imagine why the Chicago audience that first heard this symphony in this country 45 years ago walked out on it in droves, but they did. Last night it sounded by turns middle-of-the-road, slightly old-fashioned, and very exciting.

Previn and his musicians were completely on top of the large work, the brass and horns were full of massive power and the strings, piling one great sonority on another, were at their best.

The smphony demands a conductor who can keep its long ideas vibrant in the outer movements while he leads the biting scherzo and fugal writing in between with immaculate precision. Previn was superb. The last movement, which took the composer longer to write than the first three put together, has its moments of bombast, but it makes a grand point, looking back to "Belshazzar's Feast" and forward to the opera "Troilus and Cressida," to come years later.

The evening began with a beautifully molded overture to "Beatrice and Benedict" by Berlioz, done with flair. Only the Mazart E flat Symphony, No. 39, seemed largely earthbound, lacking both weight and vital style.