Washington music lovers with long memories will be able to play the nostalgia game this afternoon when a brand new musical organization, the Concert Soloists of Wolf Trap, give their first performance.

Why nostalgia?

Because pianist Earl Wild is the artistic director of the new ensemble, and his principal guest artist is violinist Oscar Shumsky. Come with me, for a few minutes, back to Washington during World War II. The Navy Band, happily faced with a sudden influx of orchestral musicians (who were being drafted all over the country), formed the Navy Band Symphony.

Its conductor, naturally enough, was Cmdr. Charles J. Brendler, the leader of the Navy Band. And into its ranks came some of the finest players in the world: concertmaster Oscar Shumsky, first viola Emanuel Vardi, first cello Bernard Greenhouse, piano soloist Earl Wild. These were musicians who had been plucked out of their usual seats at the heads of sections in Toscanini's NBC Symphony Orchestra and the orchestras of Cleveland, Philadelphia and other cities. Once drafted, they headed straight for the school of music that was being operated here in Washington for the training of musicians to serve in Navy Band Symphony, and a remarkable era of free concerts in Washington began.

Week after week in the Department Auditorium, with no admission charge, that orchestra, blessed with superb musicians who played on excellent instruments, made life more enjoyable for the vast numbers of people in wartime Washington - if, at the same time, they made things tougher for the young, struggling National Symphony.

Brendler was not much of a conductor, nor did he know his way around the complexities of the symphonic repertoire. But he had, sitting in front of him, musicians who knew not only the standard repertoire, but also many unusual works for various combinations, all of which were easy to draw from the newly enlarged orchestral resources at the Navy's disposal.

One week, for instance, Brendler's program included the Chausson Sextet for piano, violin and strings, in the orchestral version made by Frank Black. Where had that particular item come from? Wild and Shumsky had played it shortly before being drafted, with the NBC Symphony under one of its guest conductors. Since Brendler had not the least notion of how the music should go, he merely stood on the podium and beat time while the musicians in the orchestra watched and took their cues from Wild and Shumsky. When it was over, Brendler turned to the pianist and muttered quietly, "What happened?"

During those years, the Navy Band Symphony programs regularly presented all the famous and popular concertos, nearly always with Wild or Shumsky as soloists. Quite often there also were ambitious symphonies, some of them receiving their Washington premieres, all of them easily within the possibilities of the wartime ensemble.

For some in the Wolf Trap audience this afternoon, there will be ineffaceable recollections when Wild and Shumsky come onstage to open the program with Beethoven's Kreutzer Sonata. The new chamber music program came about this way.

Kay Shouse, whose generosity to music lovers in this country did not stop with her gift of the Filene Organ in the Kennedy Center Concert Hall, or of the Filene Center and it surrounding grounds at Wolf Trap, or with commissions for new works or countless other gifts, came up with the idea, a year ago, that Wolf Trap ought to have its own resident chamber music ensemble. She asked Wild to take charge of the program. Together they came up with the idea of putting together what Wild describes as "a group of verteran virtuosi with the most gifted of the younger musical generation."

There are six members in the group. Their instruments - piano, violin, cello, flute, harp and guitar - will make possible a remarkable number and variety of works both from the standard chamber music repertoire and from the world of lesser-known compositions. For example, today's program: After the oepning Beethoven sonata, harpist Gloria Agostini, flutist Gary Schocker and Shumsky playing viola will turn to the Debussy Trio. This is to be followed by a Bach solo flute partita played by Schocker, and the afternoon will close with the Tchaikovsky Trio played by Wild, Shumsky and celist Charles Curtis.

The one member of the Concert Soloists not on today's program is guitarist Eliot Fisk. However, in their second progarm, on Aug. 12, Fisk will paly a group of Villa-Lobos etudes.

Who are the other players besides Wild and Shumsky? Harpist Agostini, like them, played with members of the NBC Symphony under the baton of Leopold Stokowski, who once said, "She produces the most beautiful tone that I have ever heard on the harp."

Schocker and Curtis, both 18, are the youngest members of the group, Schocker has appeared as soloist with both the New York Philharmonic and Philadelphia orchestras. Curtis was the winner of the Bach International Competition for cellists last year.

Fisk, in his early 20s, a former student of Oscar Ghiglia and Alirio Diaz, is a Yale graduate who two years ago become the head of its new guitar department.

While chamber music is by no means new to Wolf Trap, there is more to the picture than the establishment of a resident chamber ensemble: Kay Shouse is now busy with plans for the building of a 600-seat shed designed specifically for chamber music to be ready next summer. The possibilities for new kinds of programming in such a shed (the size is the same as the one at Marlboro) are endless and add a welcome new dimension to Wolf Trap. CAPTION: Picture, Earl Wild, pianist and artistic director.