Two-thirds of the National Symphony Orchestra is taking the week off, and the result should be as refreshing to the audience as to the absentees.

With an orchestra of about 30 players and a chorus slightly more than twice that size, this year's NSO edition of Handel's "Messiah" (with a few cuts in the score) achieves a lightness and clarity that are not far from what Handel imagined when he composed the music. Under the baton of Vittorio Negri, a specialist in 18th-century music, this is a Baroque "Messiah." It does not venture into purist fussiness, but contrasts neatly with the Victorian approach that was for too long the standard approach.

The reduced performing forces bring slightly less sonic muscle to the music than would be expected from a larger group, but the sound has a focus that more than compensates for the lack of sheer volume -- which was never wanted, in even the most grandiloquent performances of the past, for more than a few numbers. As usual, the musical and emotional climax comes in the big choruses, notably "Hallelujah" and the final "Amen." These were as impressive as ever, in the perspective established by the total concept of the performance. As usual, the audience stood for the "Hallelujah" chorus -- conveniently, since it was already on its feet for a standing ovation when the chorus ended.

The Oratorio Society earned this recognition. Throughout the evening, it sang with a purity, balance and richness of tone, a clarity of diction, a precision of ensemble sound and an emotional power and sensitivity that were almost exemplary. Every syllable came across not only with total clarity but with emotional power and carefully calculated dynamics. A large measure of the credit goes to Negri, who conducted with great style and sensitivity, but the performance also reflected the excellent training the Oratorio Society has received from Robert Shafer.

At this point, it is hardly a surprise that there is an excellent chamber orchestra (in fact, several of them) concealed within the bulk of the National Symphony, but it was a pleasure to hear it performing so well in the Baroque style, which is not one of its specialties. The reduced strings had a fine lightness of tone that did not exclude richness, and the trumpets and tympani were impressive in the relatively rare moments when they had work to do.

Except for baritone Leslie Guinn, who turned in a superb performance, the soloists (all making their NSO debuts) were somewhat overshadowed by the orchestra and chorus. Tenor Gerald Grahame gave, on the whole, a fine performance, as did mezzo-soprano Diane Curry, but the impression was one of competence rather than any special excitement. Soprano Gaelyne Gabora did not have a good evening, and in general the solo singing seemed less attuned to the niceties of Baroque style than the chorus and orchestra.

There will be three more performances through Monday evening.