New York — Tonight in the Kennedy Center Concert Hall in Washington, Mstislav Rostropovich will be soloist in the US premiere of Krzysztof Penderecki's Cello Concerto, the composer conducting. The program also includes the completed sections of his new ''Requiem,'' all offered on the date of the composer's 50th birthday.
Mr. Penderecki (pronounced Penderetski) was in New York earlier this fall and we had a chance to talk about his work - but not before the specter of the political problems in his native Poland had been touched on.
''This is a situation that is not going to change. We know it now. We had some hope for the last three years, but now there's nothing we can expect. It will stay so. I can only write a 'Requiem,' which I am doing.''
He continues his busy life, composing and conducting, using his home outside Krakow as base. Wisely, he stays out of the political area, choosing rather to give people some sort of message in his music that might give them hope.
He even goes to the Soviet Union with his works, but, in his words, ''not as a politician. I go with a message for the people. It is very dangerous for artists to become involved in politics. Art is beyond politics. If I go to Russia, even in this special time now with the tensions, I am doing this for my music, for the people who like very much to hear this music. We should do it . . . it is very important.''
And just what is he up to these days? For one thing, he has closed the door on the second, neo-romantic phase of his musical progress - a quite controversial time for him. Many outspoken critics and composers have dismissed this period in his music as a sellout, as merely an attempt to write ''accessible'' music (a pejorative in these circles).
This composer, however, has never actively curried the favor of his contemporaries. In fact, when he was younger and was finally allowed for the first time to go to Darmstadt, West Germany, the mecca for contemporary music in the '50s and early '60s, he heard music that profoundly disappointed him.
''I was so bored with all this avant-garde, with all the dilettantes. I recognized the people had no background. Everything that they wrote at that time was (considered) worth hearing, and was accepted. It was very suspicious for me, because I knew the composers couldn't write a fugue!
''What has happened after 23 years is that this music has completely disappeared.''
Nevertheless, bored or annoyed as he may have been with the dilettantism, it opened up horizons and conceptions for him. As he observed, ''It was a very important period in the evolution of the music. So many possibilities, so many new conceptions, new forms, new instruments, use of tape, and so on.''
It should be noted, however, that his first celebrated work, ''Threnody for the Victims of Hiroshima'' - a searing, avant-garde 12-minute string piece that musically describes the planes flying in and dropping the bomb - was already written before his first trip to Darmstadt.
Are there composers today he respects?
''(Gyorgy) Ligeti has a (well-founded musical) background because he came from Hungary . . . . I don't like (Pierre) Boulez's music, but he is a solid musician. Luigi Nono - I don't know what to say about his music because of his political ideas, which I don't agree with, of course. We couldn't really communicate because he is a communist and I am anticommunist. I believe in God, he does not. (Luciano) Berio is a very good musician, very Italian type, very quick, brilliant, grazioso.''
Penderecki is adamant that a composer know the building blocks of music before he can forge out on his own: He has to know what the rules are before they can be broken.
''I was always concerned with the past. I wrote in the middle of the highest avant-garde - where I was myself - the 'Stabat Mater,' in '62 (later incorporated into the work that catapulted him to worldwide fame, the ''Passion According to St. Luke''). It was the first piece for me that opened up other possibilities.''
These possibilities involved incorporating the past into his work. He learned his ''past'' at the then-excellent Warsaw Conservatory and at the State Academy of Music, where he later taught.
I asked him if he still teaches. ''I don't believe anymore that I can make from someone a creative person,'' he replied, adding that ''I can teach counterpoint and orchestration,'' but that doing so won't necessarily make the student musically gifted. And he notes that he is happier spending his noncomposing time conducting, be it his own music or works by other composers that mean much to him.
One example for him - Sibelius. ''You will laugh, maybe, that I like Sibelius.'' Penderecki conducts up to 30 concerts a year, which he frankly admits is a lot for an active composer. And when he is not composing or traveling, he can probably be found digging in his garden outside Krakow. On a large plot in his 40-acre lot he has been planting an arboretum, of which he is very proud.
Penderecki is in the process of completing his ''Requiem,'' due for Stuttgart next year. He will then turn to an opera he has promised the Salzburg Festival for performance in 1986, the subject yet to be agreed on. He will then write a triple concerto (his ideal soloists are violinist Isaac Stern, cellist Rostropovich, and violinist Pinchas Zukerman).
After these projects, he will probably readdress the subject of French playwright Alfred Jarry's ''Ubu Roi,'' which he was turning into an opera buffa when the Polish problems got out of hand.
His dream piece? Probably something on the Faust legend, be it a full opera, an oratorio (a form he far prefers to opera), or a dramatic symphony. The Faust legend, and the struggle between good and evil, fascinates him.
''We are living in such a godless time,'' he said. ''I feel I must give the people a little more than only the notes, only the structure. That is why I am writing religious music. Being a Pole, living in a communist country, you know, I try to do something for the people which can give them hope.''