This is Competition Weekend at the Kennedy Center. This morning, some fortunate and greatly gifted violinist is richer by $10,000 in cash, as the result of having won last night's grueling finals in the Kennedy Center/Rockefeller Foundation Competition for Excellence in the Performance of American Music.

The winner will also be immediately in line for a recording contract valued at $25,000 plus a career management contract with engagements in this country and Europe. This adds another $35,000 to the value of his winnings. Finally, the winner of the first prize will also be eligible for a further $5,000 in cash next year simply by including a substantial amount of American music in the programs he plays during the coming season.

That last bit is logical when you remember that the whole point of this competition is excellence in the performance of American music." Every contestant is free, during the various sessions of the contest, to play some music of his own choice. But he is also required to play a high percentage of music drawn from the works of many kinds and many eras in American composition.

Begun two years ago by the center and the foundation, the competition's first year was devoted to pianists. That it has achieved some success in its chief aim can be seen in the career of the first winner, Washington-born Bradford Gowan. His first recording, on New World 304, has attracted high critical paise, which is solidly deserved both for the brilliant playing and for the unusual and strong repertoire it placed on record with music by Evett, Perie, Copland, Keeney and others.

In his appearances here in Washington since winning that first competition, Gowan has played a recital in the Kennedy Center, been the soloist in the Copland Concerto under the composer's direction in one of the National Symphony's Capitol lawn concerts, and will return this season to play the Macdowell D Minor Concerto with the orchestra on its; regular subscription series.

Last year's competition was for singers. Its finals brought out some formidable rivalry among some distinguished artists. Again a Washington-based musican won the top prize, baritone William Parker.

Parker's career was moving ahead at a reasonable rate before he won the big contest -- he had previously taken top honors in Baltimore, Marseilles and Paris and was singing with opera companies and major symphony orchestras in this country. But one of the chief purposes of the KC/RF contests is to stimulate interest in the solo recital field, for which Parker is ideally suited. The fluent easewith which he projected a broad variety of styles and moods in the songs that won him the prize was enough to mark him as the sure winner. A younger baritone, Sanford Sylvan, came in third, but it seems likely that once he has added a few more years to his present 26, he will rival Parker's achievements.

In the meantime, Parker has already enjoyed making the recording that is a part of his prize -- New World 300 (and the second recording Parker has had released on the NW label) -- and he will sing a recital in the Terrace Theater this season as a further payoff for his triumphs last year.

If the competition sponsors are right in their projections, these competitions, by spotlighting both the great solo repertoire that is available and distinctive artists who are especially gifted in that repertoire, will bring on a renaissance in that once-popular concert world, the solo recital. Tonight at 6 in the Center, the second of the weekend's contests will take place. This time the subject matter will be American compositions. The orchestra of the Curtis Institute in Philadelphia will be in the hall under the baton of composer-conductor Lukas Foss, to play the following five works, which were chosen from a semifinal field of 10 that were drawn from 54 originally submitted for the contest: "Prism" by Jacob Druckman; "Akhenaten" by Gene Gutche; "Piano Concerto" by John Harbison; "a Lyric Symphony" by Robert Wykes; and "Windsongs," which is also a piano concerto, by Ramon Zupko.

The Friedheim/KC Competition alternates annually between works for full orchestra and those for chamber ensembles. It is interesting to note that the five works to be judged tonight received their premiers from the orchestras of Baltimore, Milwaukee, the American Composers Orchestra and St. Louis, the latter orchestra having played the first performances of both the Wykes and Zupko.

That the star system prevails in the world of competitions as much as in the world's opera houses can be seen in the fact, ironic to some, that the composer of the winning work will receive a prize of $5,000 -- half the amount awarded to last night's winning violinist, not to mention any of the further goodies that run the performer's top prize up to the $75,000 rung. The second prize tonight is worth $2,000, and the third prize is $500.

Of the five composers, Druckman is the best known, a recent Pulitzer Prize winner. Gutche's music has often been heard in Washington. If Harbison, Wykes or Zupko is named No. 1, the competition will be giving prominence to composers who have been, up to now, relatively unfamiliar to most American concertgoers. Just as the competition for excellence in the performance of American music is intended to put more American works on concert programs, so the competition for composers should result in widespread performances of the works that reach the finals.

All of the Center competitions are open to the public without charge, and all of them guarantee concerts of exciting attractions.