This week's National Symphony Orchestra program, which had the first of three performances last night in the Kennedy Center, is full of happy surprises, most notably Rachmaninoff's Piano Concerto No. 2 as played by soloist Ivo Pogorelich.

In his introductory remarks, conductor Leonard Slatkin described Pogorelich's performance as "radically different" from what we are used to hearing. The pianist, he said, has "literally reexamined the work, stripped it of tradition." He might have added that Pogorelich has revitalized it; or perhaps he did when he said this interpretation is "the Edmund Morris of the music world."

The first thing you might notice about this interpretation is its duration; last night, it took 48 minutes. On the other hand, you might not notice; it did not seem one second too long, and in fact it felt less long-winded than many performances designed to show off the soloist rather than explore the music.

The closest comparison to Pogorelich's interpretation I can think of is the way Glenn Gould used to play Bach and Beethoven--as though the music had never been played before, as though the score were being read for the first time and the composer's instructions mean what they say. Any liberties taken by the soloist were far smaller than would have been expected in 1900, when Rachmaninoff composed the music and virtuoso pianists routinely treated a concerto score as a set of suggestions rather than ironclad rules.

Pogorelich's treatment differed from the usual largely in matters of tempo, phrasing, the balancing of inner voices and perhaps a few small ad-libbed elaborations, but cumulatively they had an enormous impact. The orchestra parts were the standard set, though the interpretation was--quite rightly--adapted to harmonize with Pogorelich's view of the music. The NSO clearly found this approach agreeable.

The order of performance was changed from the printed program, with the concerto placed last to avoid a sense of anticlimax in the two works by Ralph Vaughan Williams: the ultra-familiar Fantasia on "Greensleeves" and the stormy Symphony No. 4.

Vaughan Williams composed these two sharply contrasting works at about the same time, and Slatkin underlined that fact at the end of the idyllic fantasia, launching instantly into the symphony's violent opening chord without even the short pause usually observed between parts of a multi-movement work.

This symphony is probably the closest approach of Vaughan Williams's music to that of Dmitri Shostakovich: tense, angry and energetically brilliant. The NSO, which has made Shostakovich a specialty, obviously felt at home in the music--and in "Tahiti Trot," Shostakovich's witty arrangement of "Tea for Two," which opened the program.

There will be repeat performances this afternoon and tomorrow night.