Washington has a "new" orchestra that has been a familiar part of the local musical landscape for years. It has no name yet, but most people are assuming that the magic words, "Kennedy Center," will appear in the formal title. Meanwhile, some people are calling it "the mouse that roared."

Wednesday night, after being on strike for more than two weeks, the house orchestra in the Kennedy Center Opera House was joined by other Kennedy Center employes - notably stagehands and film projectionists - who agreed not to cross their picket line. The strike was settled with a compromise agreement a few hours after the secondary walkout and shortly after the ticket-sellers had voted to respect the picket lines.

In its laber dispute with the Kennedy Center (in which the key issue was whether or not it was, in fact, an orchestra) the Opera House ensemble of from 20 to 60 players rose from total anonymity to a high profile in in the city's cultural life. The house players have been criticized by Kennedy Center executive director Martin Feinstein for attempting to establish themselves as an "instant orchestra," and praised by conductor Richard Bales as "an army of generals." Here is how it all happened, and why both sides feel they've won.

"The crux of the strike was really the question of job security - tenure and an agreed-upon dismissal procedure, fringe benefits and simple recognition," says first oboist Eugene Montcoth, the jubilant chairman of the orchestra committee. "The orchestra members wanted to see their names in the program and to have a name like 'Kennedy Center Opera House Orchestra.'"

"We now have a handle on the orchestra that we didn't have before," says Alex Morr of the Kennedy Center. "In the long run, it will give us more control over the orchestra's personnel; used judiciously and wisely, it will allow for gradual improvement of the orchestra, or at least maintaining its present high quality."

The strike deadlock was broken Wednesday night when management consented to a union proposal to include nine relative newcomers to the orchestra within the contract on a probationary basis. The union, in return, agreed to withdraw its packet line and to submit the issues to binding arbitration on Jan. 1 if the contract isn't completely settled.

The nine musicians whose fate led to the breakoff of talks Tuesday have been with the group for less than the three years required for full tenture - for periods ranging from 10 months to 2 1/2 years. Under the Wednesday night agreement, they will be granted full tenure after one year of probation.

But during that period of probation, their firing procedure will be less complicated than it is for the fully tenured musicians.

Basically, in the new contract, the Kennedy Center recognizes that the musicians who have been playing there since it opened are in fact an orchestra - a permanent, professional, residential ensemble with its own group identity rather than a collection of free-lance musicians assembled for a particular musical need. The members will have job security and recognition they never had before.

In return, the Kennedy Center has won the right to audition prospective new members of the orchestra - a right it has not enjoyed before. Until now, the Kennedy Center has simply been allowed to choose a contractor, who must be a member of the musicians' local, and then allow him to select the members of the orchestra.

Under the new contract, a music director will be appointed - John Lanchberry of the American Ballet Theatre - and he will be empowered to hold auditions, to bring in musicians from out of town if members of the local do not satisfy him, and to start dismissal proceedings against musicians now in the orchestra whom he finds unacceptable.

Strictly speaking, the contract is not between the Kennedy Center and the orchestra, but between the Kennedy Center and Local 161-710 of the musicians' union. And it is not a full contract but an agreement to form an orchestra from members of the union and make a contract with certain provisions for tenure and dismissal proceedings. A last-minute compromise on these provisions on Wednesday was reached just before Feinstein left on a trip to Europe, and he took off not knowing whether the musicians would accept it.

Reached at his hotel in Paris, Feinstein said that his grim predictions about the contract had proved him an "inaccurate seer."

"I'm glad my pessimism turned out to be wrong," he said. He added that he had just ended "a very happy dinner with Mstislav Rostropovich, and the maestro is eager to get back to work."

He said that he had been particularly concerned about the future of the National Symphony Orchestra, which had voted almost unanimously, after concluding its own contract with the Kennedy Center, not to go back to work until the other orchestra was also ready to return. The final compromise offered to the musicians and accepted by them on Wednesday night "had gone as far as we could go," Feinstein said.

He added that he thought the fact that the Kennedy Center was able to put on a performance of "Semmeiweiss" after the stagehands walked out might have helped motivate the musicians to accept the compromise.

Although it is a new orchestra in terms of official recognition as part of the Kennedy Center complex, the nucleus of this ensemble has been "pretty well together since before the Kennedy Center was built," according to Montooth. Most of the members of this orchestra are also members of the Filene Center Orchestra which plays at World Trap and of the National Gallery Orchestra which is conducted by Richard Bales in Sunday night concerts in the East Garden Court of the National Gallery of Art. The National Gallery Orchestra came into existence 35 years ago, and recalling his long association Bales echoed Montooth's statement: "Many of these people have played with me here for many years - long before there was a Kennedy Center."

He praised them for the quality of their musicianship and for their versatility. "The musicians can play a musical comedy at the Kennedy Center one night and then come over here the next night and play the socks off of CHarles Ives' Second Symphony - or perform a piece that has never been played before.

"I hate to think of what would have happened up there at the Kennedy Center if this orchestra had not been available when it opened - to perform Bernstein's Mass,' for example."

Montooth noted that of the 44 members of the orchestra who have been with it for at least four years, "29 can be heard in the recording of Bernstein's 'Mass,' and there would have been more if the orchestration had been different."

Most of the members of the orchestra also teach music to supplement their income, which varies considerably according to various players' estimates. Some players earn as little as $6,000 or $8,000 per year for their orchestral work, Montooth estimated, while "others may be able to make $15,000 to $20,000 if they play in everything."

Players depend naturally on the instrumentation of the music being offered, he said. "It can add up to very little if you specialize in an instrument like the piccolo or the contrabassoon."