In the Bohemian quarter of West Berlin known as Kreuzberg, where avant-garde artists and Turkish migrant workers enjoy cheap rents and free-spirited life styles flush against the Wall, a local band called the Subtones was belting out a few tunes from the 1960s when an American fan asked if he could sit in.

Seizing the microphone in the recording studio with relish, the United States ambassador to West Germany, Richard R. Burt, let down his premature gray hair and wailed some favorite oldies such as "Teenager in Love" and "Tell Me" with backup help from group singer Tommy Lamour.

Later, after a round of beer and reminiscences about the music of the Doors and Jimi Hendrix, Burt was presented by his hosts with a tape of the impromptu jam session. "I'm going to play this to my wife all day long," the envoy gushed with a touch of pride.

Said Gahl Hodges Burt with a grimace: "I'll buy myself some earplugs."

The foray into Berlin's rock scene was not atypical for the brash young arms control expert, whose enthusiasm for heavy metal sounds is well known to his Washington friends, with whom he used to frequent Club Soda, the rock revival spot in Cleveland Park.

And once, while attending a Dire Straits concert in the divided city, Burt was whisked backstage to meet guitarist Mark Knopfler, one of his musical idols. After a friendly chat, the young ambassador gave the rock star a copy of "Deadly Gambits," the book by Time magazine's Washington bureau chief Strobe Talbott that describes the nuclear policy battles in President Reagan's first term waged primarily between Burt and his Pentagon rival Richard Perle.

West Germany's staid diplomatic circuit rarely has endured such a generation shock as occurred last September, when the septuagenarian Arthur Burns was replaced by Burt, still in his thirties, to run what is considered America's largest and most important embassy in continental Western Europe.

Burns was revered by his peers and the Germans alike as a modern-day Nestor who exuded sagacity and discretion. His fondest passions were economics, classical music and his own oil paintings, which decorated the sprawling ambassadorial residence on the banks of the Rhine.

Burt, on the other hand, had developed a reputation for irascibility and arrogance in his previous job as assistant secretary of state for European affairs and before that, as head of an interagency working group preparing arms control policy.

And even before Burt arrived in Bonn last September, he was excoriated in the West German press for purportedly urging President Reagan not to meet Willy Brandt, the leader of the opposition Social Democrats, during Reagan's state visit to West Germany last May. He stalked out of a press briefing during the Reagan trip because he was upset by the reporters' disrespectful line of questioning.

But to the surprise of age-conscious Germans, fellow ambassadors and even his own staff, Burt has managed to stifle detractors here by carrying out a "charm offensive." He has alleviated tensions with the Social Democrats by helping arrange a successful trip to Washington and a meeting with Reagan for Johannes Rau, the party's candidate for chancellor in next year's election. He appears to have defused a row with Foreign Minister Hans-Dietrich Genscher that erupted after the news weekly Der Spiegel misquoted Burt as describing Genscher as "slippery."

Much of the credit, Burt admits, goes to Gahl, whose skills as what he calls a "fantastic hostess" have enabled the couple to enjoy a honeymoon in the West German society columns.

Lately the publicity has reached what Gahl Burt feels is an uncomfortably high level, and it was only with great reluctance that she decided to join her husband in an interview to discuss their life in West Germany.

"Having Arthur Burns as a predecessor is an impossible act to follow," Burt said as he joined his wife on a couch in his spacious office. "We are trying to exploit our own advantages, our youth, in order to present a young dynamic image we hope is representative of the confidence and optimism of Ronald and Nancy Reagan."

Still, Burt's brash, aggressive nature jars members of the striped-pants community of diplomats and stuffy German officialdom. Some have grumbled that his peripatetic social profile and complaints about German parochialism make him appear too much like a viceroy. Others, including Chancellor Helmut Kohl according to some reports, are perturbed that Burt and his wife do not speak fluent German, a shortcoming they are trying to rectify through language courses.

Gahl Burt's social skills were widely recognized in her work as Nancy Reagan's social secretary, a post she regretfully surrendered to move with her husband. Washington friends say the frustrations of leaving Washington for Bonn weren't just geographical.

"It was a total change in role for her. She went from being a Washington working woman to being wife-of," says Sheila Tate, who as Nancy Reagan's press secretary worked closely with Gahl Burt, known professionally as Gahl Hodges, from May 1983 until September 1985.

The Burts married in Rome over the New Year's holidays a year ago, after a courtship that began with a discussion about nuclear jargon.

"We spent the first night talking about throw weight, so the second night I brought along a Rand bomb computer," recalled Burt, referring to a device made by the Rand corporation that contains key data of nuclear weaponry. "Later I introduced her to more important things, like [rock groups] the Yardbirds, Small Faces and Bruce Springsteen, before he became famous."

Gahl does not conceal that she greatly misses her work, and she offers vivid testimony that the plight of the Foreign Service spouse who sacrifices her career to follow her husband has become a serious morale problem for the State Department.

"It was an interesting job that I loved. I was working for a woman I admired and was crazy about and respected a great deal. She was not only my boss but offered great advice. Both personally and professionally life was really happy, so leaving was very hard. But being here is no huge burden, and we have more time together than we ever did before."

While acting as her husband's unofficial adviser, and occasionally curbing his rock fantasies, Gahl also gets to share in some of the more rewarding aspects of diplomatic life. Both of them count the release of Soviet dissident Anatoly Shcharansky on Feb. 11 as one of the most moving events in which they have participated.

Burt was a pivotal figure in early soundings about negotiating Shcharansky's freedom as assistant secretary for European affairs, and when he became ambassador in Bonn he became intimately involved in the delicate dealings among Washington, Bonn and East Berlin that culminated in the dramatic events on Berlin's Glienicke Bridge.

Burt recalled being struck by Shcharansky's remarkable good humor and open-minded view of life as he escorted him off the bridge and into a limousine. When they arrived at Tempelhof military airport, where Shcharansky would depart on a plane to meet his wife whom he had not seen since the day after their wedding in 1974, Gahl Burt offered the freed dissident a gift of wine and fruit. He tore open the package and began devouring the strawberries, expressing astonishment over their size and freshness. Later, when their plane was halted on takeoff because of frozen brakes, Shcharansky turned to Burt and said with a twinkle in his eye: "American technology? I thought this only happened in the Soviet Union."

The job as United States ambassador to West Germany has been described as one of the most elaborate postings in diplomacy. In addition to duties as envoy to Bonn, he acts as the chief American representative in West Berlin, where the United States shares ultimate governing authority as one of three western allied powers responsible for the city. The Bonn ambassador also serves as ranking civilian leader for more than 200,000 American troops stationed in West Germany and Berlin.

"If you are not careful the job will run you," Burt says when asked what is the most difficult part of the ambassador's post. "You have to depend on people to give you good advice on how to spend your time."

His route to the ambassadorship was sometimes circuitous. In 1977, Burt was assistant director of the International Institute for Strategic Studies in London and started to write newspaper "think pieces." By 1979, he was the New York Times' national security affairs reporter and well on his way to becoming controversial. He infuriated U.S. intelligence sources when he wrote a story in June 1979 about a Norwegian site under consideration to replace Iranian listening posts and U2 flights over Turkey as one means of verifying Soviet compliance with the SALT II treaty.

"You don't have to read anything less juvenile than Richard Burt to see Zbigniew Brzezinski's lips move while Burt writes," State Department spokesman Hodding Carter told The Boston Globe in July 1980. (Carter said recently his opinion of Burt has changed since then. "He's in a different world now, on the operating side. He's obviously performing very well now," Carter said.)

It was Alexander Haig who hired Burt for the State Department's politico-military affairs office in February 1981. Burt's star wobbled only slightly when Haig left. A year later, Secretary of State George Shultz put his own prestige on the line by nominating Burt as assistant secretary.

Under attack by Senate conservatives, including Sen. Jesse Helms (R-N.C.) and Sen. Orrin Hatch (R-Utah), were Burt's positions on nuclear arms control policy, arms sales to Taiwan and sanctions on trade with the Soviet Union in the pipeline dispute.

At a Senate Foreign Relations Committee meeting, Hatch also questioned Burt's meetings with a former New York Times colleague, and "her articles on arms control appearing so soon after your own meetings with her." In December 1982, Shultz personally appealed to the committee, saying that Burt "worries a lot about security."

When the White House nominated Burt for the West German ambassadorial post last spring, Helms moved once again to block confirmation until reassured by Shultz that a half dozen conservatives at the State Department would not be purged from their jobs.

Burt says he has enjoyed shifting gears from the narrow policy debates that consumed his time in Washington. "There I was a foreign policy wholesaler," he says. "Here I get to be a retailer. I go out and meet small town mayors, local reporters and businessmen and explain American policy to them on a broad range of issues, be it protectionism, Central America, military defense. It's vastly different than sitting at interagency meetings in Washington."

The Burts have capitalized on their youth to seek out dialogue with a new postwar German generation. The Americans have found, somewhat to their surprise, that young Germans are more politically conservative and more upbeat about the future than they previously believed.

"I expected far greater turmoil and self-doubt in West Germany than is in fact the case," Burt says. "I've found instead optimism and stability, and this mirrors some of the positive changes we've seen in the United States.

"Bonn is like Washington -- you can get stuck in an 'inside the Beltway' attitude unless you travel around the country. Germany is so decentralized that you need to get around to feel the pulse of people in different areas, and I sense the same kind of excitement about the future and new technology here as we have in our country."

Burt also believes that the evolving German-American relationship must move toward a mature partnership, with Germans shouldering more responsibility and not blaming the United States for anything that goes wrong. At the same time, the United States has to realize that dissenting views in Bonn do not reflect anti-Washington bias.

"We have to recognize we are partners and allies, but not twins," he says.

Gahl shares her husband's views about young Germans, but reserves her strongest opinions for what she describes as the "male-dominated nature of German society." Like other foreigners, she is amazed by the rigid store-closing laws that compel all shops to shut during lunch hours and after 6:30 p.m.

"How can a woman have a family and a job in this country?" she asks. "When I was in Washington I did my shopping at night, but here a working woman only has four hours on Saturday to do all her errands. Everything from the store hours on down predict that men will play the larger role here."

The psychological trauma of Germany's divided nation has impressed both of them deeply. "I've met people living in the West with mothers and fathers in the East who need special permission to pay a visit to attend their grandson's wedding," says Gahl. "It's difficult for Americans to understand."

As the chief American representative to West Berlin, Burt and his wife have been spending a lot of time in the divided city, not only because of arrangements for the Shcharansky exchange, but to prepare for the 750th anniversary of the city next year. The East and West sections of the city are engaged in a keen competition to see who can stage the most impressive extravaganza.

"I'm not sure how many Americans are aware that West Berlin is really an island of freedom 110 miles inside East Germany," observes Gahl. "It's a thriving, exciting place and it's amazing how they keep it going."

"But they can only do it with our help," adds Burt. "The western allies provide not just military security but economic investment as well. I just hope the anniversary does a lot to remind Americans of our responsibilities there as one of the protective powers."

Burt and his wife spend about half their time out of Bonn, making frequent speeches and public appearances in Munich, Hamburg, Du'sseldorf and other important cities and towns scattered across the country. Because of the ambassador's dual role as chief of the Berlin mission, the Burts usually travel to the divided city once every two weeks to attend business and social functions there two or three days at a time.

Unlike other ambassadorial spouses, Gahl accompanies her husband on nearly all trips and has developed a reputation as a "good trooper" willing to tackle any of the mundane duties confronting her husband. At "Doughboy City" in West Berlin, a fake replica of the western outpost where GIs practice how to defend the streets and buildings from a hypothetical assault by East Bloc forces, she donned fatigues and joined the soldiers on maneuvers.

Gahl Burt is also engaged in a major renovation of the Bonn ambassadorial residence, which she says had not been "freshened up" for 12 years. New York decorator Mark Hampton has flown over twice to offer advice free of charge, and the English chintz "Hampton look" is expected to be on display at the residence by the spring.

Neither of the Burts would speculate about the timing of their return to the United States and what they hope to do once they complete their tenure in Bonn. But they both express firm convictions about what they miss most back home.

"I miss being able to leave the office, putting on my levis and driving down to my favorite bar to eat nachos," says Burt. He also confesses to a predilection for "Mad Max" videos -- depicting the travails of life in a postnuclear world -- which so far, at least, the Germans have not publicly held against him.

As for Gahl, her yearnings are expressed more succinctly: "I miss my job."