THE FIRST PROBLEM you encounter in dealing with Rafael Fruhbeck de Burgos is what to call him in fewer than eight syllables. "In Spain," says the new principal guest conductor of the National Symphony Orchestra, "they call me Senor Fruhbeck with a terrible mispronunciation of the German name. In Germany, they call me Herr de Burgos with a terrible mispronunciation of the Spanish name." He does not discuss what happens to his name in Japan, where he is the principal conductor of one of the finest orchestras.

But everyone calls him one of the world's leading conductors. Now, he is contracted to spend at least six weeks with the NSO during the regular season. He has just completed his first week under that agreement, with two more to come immediately and three more in late March and early April.

Burgos is the name of the Spanish city where Fruhbeck (son of a German father and a Spanish mother) was born in 1933, studied the violin as a child, and became concertmaster of the Burgos orchestra when he was 13 years old.

"It was a small, provincial orchestra and very bad," Fruhbeck recalls. "I have worked my way from the lowest to the highest."

He began conducting at 17, and became the music director of the Bilbao Sympathy Orchestra when only 26. Later, he was appointed music director in Dusseldorf, in Montreal and, for 15 years, at the Orquestra Nacional de Espana in Madrid, where he lives now. In the 1960s and '70s, he became internationally famous through recordings and guest appearances, and finally decided to become a full time free-lance conductor. He has been a guest conductor with all of the world's greatest orchestras, and has turned down offers of a music director's position with some of them, because he prefers the musically demanding but non-administrative role of guest.

He began conducting the NSO in the early 1970s, "after Antal Dorati had been working with the orchestra for a while, and I noticed continual improvement. I don't know any orchestra in this country that has improved so much in those years. It began as an ordinary orchestra, and under Dorati it became a good orchestra. Since Mstislav Rostropovich has become the music director, the improvement is accelerating. Now the question is whether we can achieve excellence. Do you know how many orchestras in the world I call excellent? You can count them on your fingers and perhaps have some fingers left over."

The admiration is mutual. During his frequent appearances here, it has been noted again and again that Fruhbeck draws a specially high level of performance from the orchestra, and the members -- who can be very irreverent about some guest conductors when speaking off the record -- seem unanimous in their enthusiasn. "He's a real pro" and "not a prima donna" are typical comments; "doesn't waste time" and "simpatico but efficient" are others.

The duties of a principal guest conductor are hard to define, but include helping to fill out the performing schedule; lending the luster of his name to the orchestra; and increasing the variety of repertoire and performing styles available to the orchestra.

Hugh Wolff, the NSO's young associate conductor, examines Fruhbeck with an admiring professional eye: "Fruhbeck's whole method of rehearsing is, I think, very beneficial to the orchestra. He works a great deal on precisio, ensemble, balance and intonation, and this is what our work is all about. The orchestra likes him a great deal; they don't seem to mind that he works them very hard on small details and sometimes gets a bit impatient. Rehearsing with him is a little like going to the doctor."

"He's about as professional as anybody who has ever waved a stick at us," says one NSO member. "He knows exactly what we can do and how to get it from us with minimum strain. He could probably sell more tickets if he put more showmanship into his conducting, but he puts it all in the music, and that's where it belongs."

Some conductors do a sort of interpretive dance on the podium -- an acting-out of the music's emotional content directed more at the audience than the orchestra. But Fruhbeck is never flamboyant, always precise and clear, never leaving any doubt about what he wants. His emotional reactions are translated into musical gestures -- instructions about tempo and phrasing, entries, dynamics and balance. "If I made unnecessary gestures to impress the audience while I was standing up in front of 100 professional musicians, my face would turn red," he says.

From Fruhbeck's point of view, his chief qualifications as a guest conductor rather than a music director are love of music and distaste for bureaucratic work. "When I left the Spanish National Orchestra," he says, "I did not want to be a music director anywhere for some time. I was bored with routine administrative duties, meetings, auditions -- and of course there are hard decisions that must be made in such a position that I would prefer not to make. I had so many offers, and I turned them all down -- from Italy, Switzerland, the United States; I just turned down one in this country last week."

He hesitated to accept even the position of the NSO's principal geust conductor. "But Rostropovich asked me to do this," he says, "and how can you say no to him? He is one of the greatest musicians of this century. It is an honor to be associated with him in any way. Then the musicians' committee asked me -- and my rapport with this orchestra is so excellent, I believe we can do good work together.

"I thought about this for a long time, and I decided I wanted to work more in Washington. It is one of the most cosmopolitan and civilized towns I know. So finally, I could not say no. When I accepted the position, Slava sent me a telegram saying that 'we will be two persons together trying to push a wagon.' That is a fine description, and I will modestly try to do what I can."

Fruhbeck began his conducting career in the theater. "When I was 17, " he says, " became a conductor of operettas in Madrid, while I was still studying music and law. My father, who was a businessman, insisted on the study of law because he was not certain what kind of future I would have as a musician. When he saw that at 17 I was already able to support myself very well as a conductor, he agreed to let me stop my law studies. I was earning 150 pesetas a day, which was a very good income. For a boy of 17, it was like being a millionaire. I have never felt better than I did then."

Fruhbeck became Fruhbeck de Burgos when he began performing internationally -- specifically, when he brought the Bilbao orchestra to a music festival in France. "Look, Rafael," the orchestra's manager told him, "we must do something about this German name. I cannot explain to everyone that you really are Spanish." Having annexed the name of his birthplace ("where," he says proudly, "the best Spanish in the world is spoken"), Fruhbeck made his first international impression as a Spaniard. His early international recordings, which enjoyed a spectacular success, were of Spanish music -- notably a song recital with soprano Victoria de los Angeles and the "Three-Cornered Hat" ballet of Manuel de Falla, for whose music Fruhbeck is the world's leading conductor.

From this beginning, he has built a solid reputation as a conductor equally expert in many kinds of music. He has a repertoire of nearly 300 orchestral works, practically all of which he conducts from memory. "This is no burden to me," he says, "since I have an almost photographic memory; I can close my eyes and practically see the score."

The specialties for which he is best known vary from one country to another. Outside of Spain, there is still some emphasis on his Spanish repertoire, and he accepts this as a distinction but not as a limitation. "There are not many Spanish conductors," he says, "and people in other countries like to hear a Spanish interpretation of De Falla or Albeniz." In Madrid -- where he lives with his wife and two teen-age children -- he is a champion of Bach's music and has established a tradition of performing the "St. Matthew Passion" annually in German.

One of his ambitions is to conduct more music of Spain's Golden Age -- the polyphonic vocal music of such composers as Victoria, Morales and Encina. He has established an impressive reputation on recordings as a conductor of choral music with orchestra -- not only the "Carmina Burana," which has become one of his specialties, but also Mozart's "Requiem" and such oratorios as Mendelssohn's "Elijah" and Haydn's "The Creation." A proposal for a complete recording of Haydn's Masses is under discussion. If it becomes a reality, it should find a particularly enthusiastic audience in England, where Fruhbeck is known primarily as a choral conductor.

Despite some distinguished operatic work (including a recording of "Carmen" that won critical superlatives), Fruhbeck has no plans for operatic work in the immediate future. "Next year," he says, "I will do Manuel de Falla's 'La Vida Breve' with the National Symphony, but I am in no hurry to return to the theater.

"Today, I think there is too much emphasis on stage directors and too many stage directors who merely want to make a sensation rather than respect the inherent style of a work of art. They compete to outdo one another in outrageousness, and if there is a scandal about the directing the director thinks, 'Good; it will make me famous.' When I am invited to conduct an opera, I am very careful to see who is the stage director."