THE TELEGRAPH message is headed "routine," dated May 16, 1943, and signed "HOOVER." It is typed on a standard FBI message form:

APPROVAL GRANTED TO INSTALL A MICROPHONE SURVEILLANCE ON RUTH BERLAU AT CHALET MOTOR HOTEL, THREE TWO ONE TWO WILSHIRE BOULEVARD, SANTA MONICA, PROVIDED FULL SECURITY ASSURED.

At the time, Ruth Berlau was the mistress (in the FBI's discreet terminology, the "girl friend") of Bertolt Brecht, author of some of the most striking theatrical works of the 20th century: "The Threepenny Opera," "Mother Courage," "Mahagony," "The Caucasian Chalk Circle" and "The Good Woman of Szechuan," among them.

By 1943, Brecht also was the subject of a bulky FBI file, compiled by direct surveillance, wiretapping, the use of informants and a monitoring of his mail. The file was never used for any legal action, but it is now providing an ambivalently happy hunting ground for Brecht scholars.

During the International Brecht Symposium recently held with the aid of the National Endowment for the Humanities at the University of Maryland's Center for Critical Studies, some scholars who have been using this material got together to compare notes and conjecture about what else may be in the FBI files, still unavailable for examination.

"I have a 1973 letter from FBI Director Clarence Kelley that says the Brecht files 'consist of approximately 1,000 pages,'" said Professor James K. Lyon of the University of California, pulling a photocopy of the letter from a crammed Manila folder.

"Five years later, in Berlin, my colleague Raymond Wolff received a letter from the FBI saying that there are only 427 pages," and out of the folder came another photocopy. "I have 428 pages and they don't look complete to me. Sander Gilman of Cornell has been obtaining Brecht material from the FBI, too, and the three of us have been comparing what we have. Sometimes the FBI will blot out part of a page while copying this material, to 'protect its sources'-but the parts blotted out when copying for Wolff and Gilman are often different from what they blotted out when copying for me."

From the viewpoint of a research scholar, said Lyon, the FBI files are a combination of "pure garbage and gourmet food-they threw in everything, rumors and anecdotes, including some anecdotes that actually belonged to someone else. For example, the FBI file says that Brecht was arrested and tortured by the Nazis and that he escaped from a Nazi concentration camp disguised as a woman. His friend Lion Feuchtwanger did that; Brecht was never imprisoned by the Nazis, although they would have liked to get him.

"The FBI reports everything without evaluating it, in an objective, legalistic style that makes it all appear uniformly factual. They're always careful about terminology-for example, they never call Brecht a Communist but a 'suspected Communist' or a 'suspected agent of the Soviet government.' On something like that, they bend over backward, but they never separate fact from opinion. Sometimes that makes the file scary."

Raymond Wolff, an American doctoral candidate at the University of Berlin, also has been studying the Brecht files of the CIA and its predecessor, the Office of Strategic Services (OSS), and he reports that these files are less careful about name-calling: "The OSS sometimes quotes sources that call Brecht a Communist-there were plenty of people in postwar Germany who would have been willing to say that-but, on the whole, these files are more careful than the FBI's.

"The OSS did analyze and evaluate its material, and it had some quite sophisticated, scholarly people working for it-a lot of Harvard types. Herbert Marcuse worked for the OSS for a while, although he never worked on the Brecht file. In its analysis of the Council for a Democratic Germany, a wartime exile group that was working to influence the formation of Germany's postwar government, the OSS considered Brecht one of the two or three Communists inthe group."

Strictly speaking, Lyon said, "Brecht was a Marxist but not a Communist; he never joined the party and was too much of an individualist, too distrustful of authorities of any kind, to follow a party line.

"Paul Tillich, chairman of the Council, summed it up. Asked by the FBI about Communist membership on the Council, he told them: 'We have 2 1/2 Communist representative on the Council; the half is Bertolt Brecht.' This may have exasperated the FBI, but it is perhaps the most valid description of Brecht in the file."

John Fuegi, director of the Center for Critical Studies, is one of the founders of the International Brecht Society and coeditor of its yearbook of Brecht studies: Brecht Today. Somes of his recent research has turned up material that underlines Brecht's independence of mind: three unpublished poems on Stalin that refer to him as "der fuehrer," "the tsar" and "the venerated murderer of the people."

"In one of these poems, Brecht says that Stalin has 'forgotten the Communist Manifesto' and slapped Lenin's face," Fuegi said, "and then he calls him 'Terrible' in a clear reference to Ivan the Terrible. These poems are not in the 20-volume edition of Brecht's works probably composed after Stalin's death, but they certainly predate the anti-Stalinist movement that began with Khrushchev's denunciation of him in 1956. I have spoken to an acquaintance of Brecht's who recalled seeing this material in 1955."

Brecht always has been elusive-physically as well as metaphysically. In 1933, on the day after the Reichstag fire, he left Germany and began a long period of cantankerous exile, waging a constant war of words against the Nazis, during which, he said, he "changed countries more often than my shoes." At first he stayed close to Germany, principally in Scandinavia. "We sit restlessly, as near the border as possible, waiting for the day of our return," says one poem of this period, written in Denmark.

But as the German armies came closer, Brecht finally moved to Los Angeles in 1941 and became a subject for FBI surveillance on two counts: as a German national and as a suspected Communist. Reflecting this double-edged status, his file was originally labeled "Enemy Alien Control," but the category was later changed to "Internal Security." He was suspected not only of trying to promote the future of communism in Germany, (a charge that might be true, properly understood) but also of espionagem, which now seems ridiculous. Much is made in the FBI file of the fact that his mistress purchased a lot of photographic equipment. The file reports at one point that "Her effects reflect that she has done extensive photographic copying of German language poems, etc. (no doubt the work of Bert Brecht)," but elsewhere says that an informant "was unable to determine the nature of the material copied onto this film."

Until the release of the FBI material, according to Lyon, the period of Brecht's exile was "one of the most obscure in his life." Now, researchers have access to his bank records, to telegrams and phone conversations-even to a few letters from his mistress, which Brecht, as a prudent husband, had destroyed. Also included (in whole or in part) are half a dozen letters and a telegram by Brecht available from no others source. In the same file are precise if non-literary translations of some of his Marxist writings; a detailed, accurate summary and political analysis of his play, "Die Masssnahme " ("The Disciplinary Measure"); an anonymous informant's statement that "Brecht is looked upon by German Communists as their poet laureate," and an estimate by the U.S. Attorney at Los Angeles that Brecht "appeared to be a proletarian, bordering on an anarchist."

It was formerly believed by Brecht scholars that his years in the United States represent a period of political inactivity (most unusual for his highly political person). The material now available makes it clear that he was very active in this period-but in exile politics, not in Communist or American politics. American Communists, in fact, felt somewhat uncomfortable about Brecht; one of their journals had denounced him in 1937 as "an individualist in collectivist clothing" and during his stay in this country he was accused of "arrogance and superciliousness toward his comrades in the U.S.A.," according to Lyon.

Brecht left the United States immediately after testifying before the House Un-American Activites Committee on Oct. 30, 1947-bringing with him a microfilm copy of all his manuscripts. During the six years he had stayed in this country, the FBI had never actually gotten around to talking to him, althouth it had certainly listened to him, via wiretaps (euphemistically called "technical surveillance" in the files). Brecht was aware of this surveillance, as was graphically demonstrated on one occasion when his wife called a friend and began reading recipes to her from a cookbook-in Polish, a language she did not speak. Somehow the anecdote (known from Brecht's acquaintances) did not find its way into the files (or into the material so far released to scholars), but shortly thereafter the "technical surveillance" was lifted.

In 1947, the FBI learned that Brecht was planning to leave the United States and the Los Angeles field office requested permission "to interview Brecht concerning his contacts with Gregori Kheifets, former Soviet vice consul in San Francisco and alleged NKVD agent." J. Edgar Hoover gave permission, but a few days later learned that Brecht was under subpoena to testify before HUAC and instructed his agents to wait until after the HUAC appearance. The FBI was unaware for nearly two weeks that Brecht had left the country the day after his HUAC testimony; and by the time Hoover instructed his men on Nov. 12 "to interview subject without undue delay," Brecht was long gone. Lyon rather regrets that the interview did not take place, believing that it might have been a "historic" confrontation, as the HUAC session was.

Even without such material, however, the file is helpful in dating precisely when Brecht worked on various literary projects, in listing the Hollywood people with whom he had contacts and even in providing details on projects that never materialized, such as a film based on a modernization of Aristophanes' "Lysistrata."

Information on his checking account in the FBI file contributes directly to a knowledge of Brecht's character and his circumstances during his American stay. After suffering some deprivation at first, he was relatively well off in his later years here, although he tried to cultivate the image of a neglected, struggling artist. It is true that the Brechts were obliged to live on $125 a month during their first year in America, Lyons said, but it has not been generally known that they were later able to buy and pay for a spacious two-story home in Santa Monica, or to afford hired help. The file also indicates that Brecht did not tell his wife about all the money he earned-probably so that he could use the unaccounted funds to support Berlau. "His checking account information also reveals the great generosity of both Brecht and his wife toward friends in American and those in postwar Europe to whom they were sending packages after 1945," according to Lyon.

After his return to East Germany, Brecht was lionized and financially subsidized but also regarded with some suspicion by a Communist government that had as much trouble as the FBI in deciding what made him tick. Brecht himself had no such trouble. When he saw his end approaching, he used his considerable influence to secure the burial spot he wanted-directly across from Hegel's grave in a cemetery that had stopped admitting new customers.

He was less successful in securing his desired epitaph. He asked that his tombstone should read: "I hope that because of my life, the powerful will sleep less comfortably." The tombstone actually reads: "Bertolt Brecht: 1898-1956." The absence of any other inscription undoubtedly means that he has made the powerful sleep less comfortably. CAPTION: Pictures 1 and 2, Brecht in 1931, and at right Hoover in 1967.