Sarah Caldwell yesterday was named music director of Wolf Trap Farm Park, a new position created specifically for her -- and one that will not interfere with Caldwell's position as artistic director of the Opera Company of Boston, which she founded in 1957.

Caldwell, 51, who has been in negotiation with Wolf Trap officials for several months, said yesterday, "I'm delighted with the prospect of this new challenge in my life and hope that in my own way I will be able to contribute to the ever-increasing cultural role which Washington plays in our country's life. I know I will have the full support of Mrs. Jouett Shouse in this endeavor."

Some area musicians are already speculating about the influence Caldwell will have on the music scene. There have been reports that she might institute seminars in choral conducting and special sessions for young musicians along the lines of classes at the Berkshire Festival in Tanglewood, where she first came in contact with much of the music world.

Mrs. Shouse, founder-donor of Wolf Trap, was enthusiastic about the new appointment. "All at Wolf Trap are delighted to have Sarah Caldwell join our staff," she said. "We are counting on her expertise and imagination to add even wider interest in our programs, which now extend beyond the summer months."

Caldwell has occupied an increasingly important role in this country's major musical activities during the past decade. In the season of 1975-76, she was the first woman to conduct at the Metropolitan Opera, made her debut conducting the New York Philharmonic and had her picture on the cover of Time magazine.

At the moment Caldwell is in New York City, where her preparations to stage and conduct Verdi's "Falstaff" next Friday with the New York City Opera Company are stymied by a strike that hit that organization Sunday. Caldwell is no stranger to controversy. In her Boston years, she has at regular intervals taken on heavy debates over her productions of such important new operas at Nono's "Intolerance," Schonberg's "Moses and Aaron" and Roger Sessions' "Montezuma," all of which had their U.S. debuts under her direction.

Mstislav Rostropovich, music director of the National Symphony Orchestra, which plays a series of summer concerts at Wolf Trap, had high praise for Caldwell yesterday. He announced that she has already been engaged by the National Symphony to conduct its Fourth of July concert next summer on the west lawn of the U.S. Capitol, where the orchestra played four programs this year.

"Sarah Caldwell is a very great personality and a great musician," Rostropovich said yesterday. "I am glad Wolf Trap now has a great musical head, which it has needed. The National Symphony will of course continue to participate in the summer programs there. Some things for next summer had already been planned and there are contracts we have to go ahead with." One of the concerts to which Rostropovich referred is a projected Verdi Requiem under the baton of Rafael Fruhbeck de Burgos.

Caldwell, who has appeared at Wolf Trap as guest conductor with the National Symphony for the past two summers, has not yet announced details of her plans. However, it is rumored that she will bring several productions of her Boston company to Wolf Trap.

It was a production of the Opera Company of Boston that first brought Caldwell to Wolf Trap five years ago. In 1974 she directed and conducted Prokofiev's "War and Peace" there, expanding her Boston production to fill the larger stage in the Filene Center. Late next spring Caldwell is staging Verdi's "Aida" and Wagner's "Flying Dutchman" in Boston. Shirley Verrett will sing the title role in the Verdi for the first time in her career, and Simon Estes will take the title role in the Wagner.