The program was labeled "Music of Black American Composers," but the music in last night's concert at the Terrace Theatre sounded as various and as solidly in the American mainstream as it would have from a random selection of composers. There is no reason why a black composer has to "sound black," and in these works these compsers chose simply to sound modern. The works had only one element in common: All of the music was more or less contemporary, ranging in date from 1984 (Ulysses Kat's suite from the sound track of "The Quiet One") to 1975 (George Walker's nobly meditative "Lyric for Strings" and David Baker's brilliant Concerto for Cello and Chamber Orchestra). Otherwise, they differed as readically as Samuel Barber from Luciano Berio.

A concert dedicated to black classical composers has to focus on contemporary music, because the majority of recognized artists in this category are still alive. This means that a concert of black composers can effectively demonstrate (as last night's concert certaily did) the great variety of musical styles available in America today. It also demonstrated that black composers, as a group, are at least as talented as those of any other ethnic background -- but surely nobody doubted that.

The concert, presented in cooperation with the Kennedy Center's cultural, diversity program, was the first performance by conductor Stephen Robert Kleiman and the National Chamber Orchestra, a new ensemble that turned out to be essentially a familiar group working under a new name. Until fairly recently, Kleiman and his orchestra performed at the National Academy of Sciences under the name of the New World Players. There, the concerts were free; in the Terrace, they are not, and judging by the empty sears at its Kennedy Center debut, the National Chamber Orchestra has some serious audience-development work ahead. The quality of what it did night indicates that such an effort will be worthwhile.

The performances last night were always capable and sometimes exciting -- a fine achievement considering that the six works on this 2 1/2-hour program were all quite unfamiliar,including a world premiere (Howard Swanson's "Vista No. 2") and two Washington premieres (Kay's suite and Carman Moore's "Youth in a Merciful House"). Rehearsal time for orchestra is always expensive and therefore limited. Added rehearsals might have made this concert a bit more exciting, but it was musically eloquent and precise.

The most impressive work on a program that had no real weaknesses was Baker's concerto, which received a brilliant performance from cello soloist James Herbison. In its final movement, Baker's music ventured into jazz, a field in which this compsoer has a substantial reputation. But even then it did not proclaim itself as black music; its syncopated rhythms and big-band haronies were jazz assimilated to classical music, with the cellist soundingf not unlike Stephane Grappelli playing an octave lower. A significant part of the music's impact in this dazzling movement was derived from its modulations between jazz and classic idioms.

There was also a trace of jazz in the Introduction, Cadenzas and Interludes of Hale Smith, another composer with a solid jazz reputation. But the jazz elemnt did not reside in the occasional blue notes heard from the piano; it could be heard in the frequent solos, which alternated with orhestral interludes and bits of one-on-one dialogue between the players. This was the spirit of jazz sublimated and transformed into an atonally melodic idiom with a different and equally (but not more) valid alanguage, momentum, energy level and sense of disciplined freedom. It is superb music and it highlighted effectively the fine solo ability of some of the orchestra's memebers.

George Walker's "Lyric" had the polish formal grace and deep emotional communication that ae hall-marks of that composer's work. Kay's Suite was Hollywood, refined and rearranged but perhaps not trimmed quite as thoroughly as it might have been. Swanson's "Vista" might have been revised and thighenedif the coposer had not died before its long-delaued first performance; but even with some moments of looseness or repetition it achieved considerable power.

The most experimental work on the program was Moore's piece, composed for the curious combination of flute, viola, two bassoons and two percussionists. It is a bright, energetic work with lots of color and it might profit from a more focused sense of structure.

In its diversity, its general level of musical quality and the professionalism with which the music was treated, this concert was a delight for connoisseurs of new music and coul have offered some rare moments even for the most conservative tastes. From the announcements of its forthcoming concerts, the National Chamber Orchestra is planning to cultivate mostly the rocky soil of modern music. If this program is a fair sample, it is likely to find some fascinating material there.