Composer-conductor Gustav Mahler talked about being "condemned to the Hell of the theater," and frequently longed, in his letters, for "the peace of my little house in the meadows which is brand new and an ideal resort: not a sound in the vicinity! I'm surrounded by nothing but flowers and birds which I see but don't hear." In that secluded mountain spot which he nicknamed the "tiny house," Mahler wrote his second and third symphonies.

Several years earlier he had written to his friend Fritz Loehr, "Everything has happened as usual. I have willingly let myself be loaded with innumerable chains, and thus have again fallen into the usual humiliating slavery." This outburst came shortly after he took the job of music and choral director in the Kassel Theater.

"Now the conducting's over and will be for seven months," composer-conductor Leonard Bernstein told a gathering at the University of Chicago in February 1957, "while I write another show. A rather serious and tragic musical comedy for Broadway -- figure that one out." The product of those seven months turned out to be "West Side Story," universally recognized as well worth whatever amount of time it took to write.

"Four months of vacation!" Mahler wrote to his parents in 1888 when he was named director of the Budapest Opera at the early age of 28. Vacations had already become the only time in the year when he could write out the music that crowded his brain all year long.

And Bernstein, seven years after his talk in Chicago, was again ready for a break in his career as conductor, a career that had by then taken him to the music directorship of the New York Philharmonic, a post which, in one of history's striking coincidences, had belonged to Mahler for two years. In 1964 Bernstein took a temporary leave of absence from the Philharmonic. At the end of that hiatus, he wrote, "The great benefit of a sabbatical year is not so much that it affords a rest from one's labors as that it provides the glorious luxury of time to meditate, off-schedule, at ease, and without fixed limits."

Mahler-the-composer did almost all of his creative work in the summer months when he was not tied up in leading opera companies in Prague, Kassel, Hamburg, Budapest, Leipzig, Vienna and New York. Nearly all the song cycles and symphonies were written during those brief periods of quiet that separated the hectic months when Mahler-the-conductor was becoming one of the great immortals in operatic annals. Increasingly often those summers were narrowed from four months down to a feverish two. Yet from them we have the nine finished symphonies, the unparalleled song-symphony, "Das Lied von der Erde," and the Tenth Symphony, much of it completed by Mahler, nearly all of it ready to be finished (as it has been recently by two different music scholars).

Would we have had more music from Mahler had he been free more of the time to write? It would be a mistake to rush in with a positive "Yes!" Mahler-the-conductor was demon-driven to conduct not only the masterpieces of Mozart, Beethoven and Wagner, but also the lovely if lesser scores of Tchaikovsky, Smetana, Halevy and many others.Bruno Walter suggests that the creative fires in Mahler were stoked by the passion that made him so powerful a genius in the theater.

In Mahler's time, some critics said, "Mahler the conductor belongs in the first rank of his profession, but he resembles the others in that he is nothing of a symphonist. All of our great conductors -- Richter, Bulow, Levi, Mottl, etc. -- either have themselves eventually recognized, or have proved, that they were not composers."

Bernstein recalls Walter's view of Mahler when he says of his own dual pursuits, "Because half the time I cease to be a creator and switch off that magic little off-and-on switch and become a performer again, perhaps I thereby earn a certain kind of objectivity that I otherwise might not have."

It is obvious that Mahler had the same kind of off-and-on switch. "Strange!" he wrote to Bruno Walter. "When I hear music -- also while I am conducting -- I hear quite definite answers to all my questions, and am completely clear and certain. Or rather, I feel quite distinctly that they are not questions at all."

It is also obvious that there are some people around today who are as willing to try to limit Bernstein as those Viennese critics of Mahler were to insist that Mahler-the-conductor was great, but couldn't they simply skip Mahler-the-composer?

John Briggs, an early Bernstein biographer, has pointed out that pianists praise Bernstein the conductor; conductors laud his composing; and "serious" composers suggest that his real forte may be jazz.

For some years now, Mahler's own confident prediction concerning his music has been realized to a degree that even Mahler probably could not have imagined when he said, "My time will come."

Today, nearly 70 years after Mahler's death, it sounds as if the music world could not get enough of his music.

Recently Bernstein-the-conductor announced another sabbatical, this time for the entire year 1980. He says candidly, "I have no idea what I am going to compose. There is all this pressure to write an opera. I would love to write an opera. But I do not know what will come out of this year."

Mstislav Rostropovich, who had to do some heavy realigning of the current National Symphony season when Bernstein announced that he would do no conducting in 1980, said, with philosophic honesty, "Leonard Bernstein is a great composer and he must have time free to compose. I am sure that something wonderful will result from his taking this time off."

Already Bernstein-the-composer's symphonies have entered the repertoire, though some conductors still have to make their acquaintance; "MASS," which he wrote for the opening of the Kennedy Center in 1971, has been seen and heard around the world; "West Side Story" is one of the biggest hits in history on the stage, in films and on records, and it will return on Jan. 1 in a restaging at the Kennedy Center on its way back to New York.

"Songfest," is, in Bernstein's own words, "not a first-time piece." For those who have come to know intimately this extraordinary collection of orchestral song settings of American poems, it is unique and irreplaceable.

There is a postlude to all this: Mahler and Bernstein, though the most famous, are not the only men of genius to face the dilemma of the composer-conductor. In Mahler's time Richard Strauss had become equally great in both fields, regarded as superb in his handling of the operas of Mozart and Wagner as well as his own. But Strauss, except for a four-year term as director of the Vienna State Opera, never let himself become as closely involved with the intricate mechanisms of an opera theater as did Mahler. Even his Vienna years were shared with Franz Schalk.

A more recent parallel exists: Pierre Boulez, who, by succeeding Bernstein as head of the New York Philharmonic, placed himself directly in the line of Mahler and Bernstein as composer-conductor.

How does Boulez fit into this picture? As a composer he has consistently been what neither Mahler nor Bernstein was: a leader of -- and often a spokesman for -- the most extreme avant garde. A student of Messiaen and Rene Leibowitz, sometimes a champion of Stockhausen, and in some techniques a follower of Anton Webern, Boulez has contributed a slender list of compositions to the world -- perhaps 18 works, over some of which he worked for years before achieving a final version. A laser-bright dissector of anything he touches, Boulez-the-composer has not yet influenced any large public.

Boulez-the-conductor -- who once told me that he had come to admire highly two things in this country: rented cars and bourbon -- served the Cleveland Orchestra for several years before and after the death of George Szell. From 1971 to 1977, he was music director of the New York Philharmonic. Some in that city, fearing an onslaught of Webern, Xenakis and Stockhausen, were surprised to be handed a festival of Liszt along with substantial doses of Wagner and that Mahler whose music, Boulez informed me, was almost totally unknown in the Paris in which he grew up.

Boulez also took a brief flier in opera, conducting Wagner in the sanctum of Bayreuth, and Debussy's "Pelleas et Melisande" at London's Covent Garden.

It is, however, neither as a composer nor as a conductor that Boulez is likely to enter the annals of music except as a conductor of the repertoire he is now encouraging in the role for which he left the Philharmonic. He is now director of the highly controversial center for research in new music called IRCAM, located in Paris. He seems to have removed himself from the dilemma of the composer-conductor, leaving that troubled arena clear for the man who seems to have the best solution for it in today's world.