National Musical Arts is a modest group, one of the many ad hoc chamber music ensembles proliferating now in this area. Basically it is a string ensemble, with other soloists joining from time to time as the need arises. Most of the time it does not play with the polish of the finest in its field, but that is all right, given the fact that chamber music is hardly the right vehicle for narcissistic virtuosity.

That said, then we mention the high point of its program Saturday at the National Academy of Sciences. There wasn't anything modest about it when Loren Kitt, the first clarinet of the National Symphony, joined the group for Mozart's E-flat-major Trio for clarinet, viola and piano. Kitt is quite simply one of the finest wind players now performing. He is one of the orchestra's stars, and with him working here, it is important that we hear him in chamber music as much as possible.

Mozart, of course, had a love affair with the clarinet. He wrote most of the best music that there is for the instrument (though Brahms helped out a little later). This trio, less well known than the clarinet concerto and the quintet, is full of those refulgent inflections of phrase that are characteristic of the great man's humanity at its peak; this is "Marriage of Figaro"-class music.

Kitt's playing sounded like the best Mozart singing. Passionate understatement prevailed. Note values were precisely calculated and dynamics were exquisite.

Later in the program he also played Stravinsky's tiny little Three Pieces for clarinet. After the Mozart, they were no more than afterthought.

Gabriel Faure''s flowing and ardent Piano Quartet had its rough moments, but what a pleasure it was to hear it at all. It was also nice to hear Koda'ly's Duo for violin and cello, however rough the execution. The players were violinist Rebecca McMillan Green, violist Karen Dreyfus, cellist Jack Kirstein and pianist Patricia Gray.