"During my first 50 years, in the Soviet Union, I must say I considered myself one of the privileged members of the society," observed pianist Bella Davidovich last week in Philadelphia. She was there preparing with the Philadelphia Orchestra the seldom-heard Rachmaninoff First Concerto, in which she will make her Washington orchestral debut tonight.

"Musicians are not quite as privileged in Russia as people in the ballet, or the circus or the cinema, but musicians lead enviable lives, at least within the limits of the possibilities," explained the distinguished musician who earned the title of "Deserving Artist of the Soviet Union." "That is next to the highest level of state honor. Only two who have left carried the higher honor, which is National Artist of the Soviet Union, and one of them is Slava National Symphony music director Mstislav Rostropovich ."

Davidovich, 53, was the only woman among the half dozen or so leading Soviet pianists.

In Russian she recounted in gripping detail--with frequent interjections in English of "It is unbelievable!"--as an assistant translated, the exhaustive limits of the "possibilites" that were imposed upon her and that eventually led her, a widow, who knew almost no one in the United States, to emigrate here in October 1978. She brought her mother and sister and joined her son, who had come a year and a half earlier. She had never been allowed to tour here, despite her enormous reputation, particularly as an interpreter of the early romantics like Chopin and Schumann.

Unlike most of the other familiar Soviet e'migre's, who have enriched artistic life here as persons fleeing the Nazis did four decades ago, Davidovich took a tremendous chance with her career when she emigrated. When Rostropovich came West he was very famous here; not Davidovich. When she arrived at her present one-bedroom apartment, at Kew Gardens in Queens, 12 miles east of Manhattan, there was little stir. The neighbors, who had no idea who she was, would pass notes under the door asking her not to play her piano so loudly. "Now they will ask ahead when I am going to be playing and stay home to listen," she noted with some satisfaction.

But news spread in American music circles by word of mouth, and by the time of her U.S. debut a year later, Carnegie Hall was sold out. Critics agreed that a major artist had arrived. Since then she has recorded frequently.

Her fame began when, while only 21 and still in the conservatory, she won Poland's 1949 Chopin Competition, one of the major contests.

Then the commissars began to impose unexplained limits on her foreign travel, one of the constraints that led her eventually to leave her country. "When I finally got back to Warsaw it was nine years later, and I did not know until then that they had asked for me to play many times and had been turned down by the Russians. When I finally got back they ran a huge portrait in the main Warsaw paper saying, 'After Nine Years.' Because of Gossconcert, the Soviet bureau in charge of foreign engagements, the first time I went to Poland I was just a girl and a student, and by the time I returned I was already a widow." In the interim she had married Yulian Sitkovetsky, a leading Soviet violinist who died of cancer at the age of 32 in 1958.

Davidovich found that within the Soviet Union she was free to play whatever she wanted and wherever she wished, including regular engagements for 28 consecutive years with the Leningrad Philharmonic, the leading Russian orchestra. "And I was one of the few to be asked to play in the Great Hall of the Moscow Conservatory, which is a great honor. But even there, as a Jew, I was very slow to be admitted to the faculty. And the goverment seemed to allow me to go to the West unwillingly. I had lots of invitations to the West, but they would never tell me. I finally visited Italy four years in a row and they also let me go to Holland. Meanwhile, I traveled to East Germany 15 times."

But it was not artistic discrimination that led her to leave; it was her family. "The first reason was my son. To have only one son, to lose my husband so long ago--it was natural. I had to move sooner or later to be with him." Dmitri Sitkovetsky, who has followed in his father's footsteps as a violinist, abandoned the Moscow Conservatory in May 1977 to study with the renowned Ivan Galamian at Juilliard.

"My son had been talking to me for two and a half years about leaving. And he was very angry with his mother for not wanting to leave. After he left, the tours to the West were still permitted in 1977. They knew that I was not the type to go away and leave my mother and sister behind. So I had hoped for the best. But then all my 1978 tours were canceled. No explanations were given and there was no need to ask. It was clear that my son was the reason and that unless I left, I would never see him again.

So Davidovich, her mother and her sister applied to emigrate, and after the standard six-month wait their wish was granted. But the actual departure was very difficult. "Most everything had to be left behind. The law then, for instance, required that I could only bring out music that was published after 1946, which ruled out most of my repertoire. Now the latest law requires that you can bring out only things published after 1975. And you could bring out books only in packages of 12. And it was impossible to bring out more than one copy of any recording. Most of my personal things I distributed among family and friends. I had two pianos and they wanted brought out only my Soviet-made piano and not my Bechstein, and it was such a big problem with the packaging and taking it to the duty office, it was just too much trouble. Two years later someone finally got out my Bechstein into Canada, and I went to Toronto to meet it." Now in concerts Davidovich (prounounced "Da-vee-DOH-vitch") plays a Steinway.

Davidovich, a graceful person with bright red hair framing an angular face, said that the risk she took in starting a new career here did not frighten her. "I didn't think about it, she explained. "I decided I would just play. And the rest would happen as it happened."

She is an intimate, lyrical artist, described the other day by one of Washington's most respected experts as "a Myra Hess-kind of pianist," referring to the late British performer.

Asked to describe her style, she paused, then said: "My goal is always that the piano should sing so that it will not sound percussive. It should sound very intimate. It should be possible to communicate as a voice."

Tonight's program of Rachmaninoff with Eugene Ormandy and the Philadelphia Orchestra is yet another artistic milestone for Davidovich. The Philadelphia was very much Rachmaninoff's orchestra; it was the orchestra with which the composer made all of his orchestral recordings, and to which he dedicated his last symphony. Moreover, in three of Rachmaninoff's four concerto recordings Ormandy was the conductor. "I had played with Mr. Ormandy twice in Europe, but when this program was arranged I had simply submitted a list of works that I could do, and it was he who picked the Rachmaninoff First from it." Being asked by Rachmaninoff's disciple to play this work is no small compliment. Not only will it be done here and in Philadelphia but also in New York later this week.

"When I heard that all the concerts were sold out, I was very excited, but then my mother put me in my place. She said, 'My dear, they must be sold out because it is Ormandy and the Philadelphia and you should be thankful you are playing with them.' I suppose that she is right."

Asked if she yet feels "at home" in Western society, Davidovich is so hesitant that it is clear she is not yet entirely at home. She points to difficulties such as the need for visas to go everywhere, because it will be another year and a half before she can become an American citizen. And managing those way stations of the touring performer, hotels and airports, still comes to her with difficulty. Her command of English is also limited.

But three and a half years after arriving here unknown, she is once again a celebrated artist.