THE YOUNG Howard University opened the letter from George Gershwin inviting him to audition for a play called "Porgy and Bess." Todd Duncan muttered, "Who's Gershwin?" checked his calendar, noticed a prior church engagement, and replied "no."

Gershwin, who had been interviewing hundreds of candidates, just invited the singer again. Now Duncan was curious. He'd heard of Gershwin, of course, but considered him something of a lowbrow, just a Tin Pan Alley composer. Duncan was more of a Brahms or Strauss man, himself. But this time, his interest was piqued. He took a train to New York one weekend in 1934.

"Where is your accomponist?" asked the composer.

"Can't you play?" asked Duncan.

Only a few minutes later, Gerswin turned from the piano, interrupted Duncan's rendition of an Italian folk song and pronounced, "You're my Porgy."

But although Gershwin knew he had found Porgy, which was to be one of the most important roles for a black on the stage in this century, Duncan wasn't so sure. And he answered cautiously, "Well, I don't know whether I could or not . . . I'd have to hear your music." Still undaunted by the singer's indifference, Gershwin invited him back the next Sunday. Duncan asked him for the carfare.

The next week, Duncan performed for a room full of Gershwin's friends. Then Gershwin and his brother, Ira, sang their score.

"George and Ira stood there with their awful, rotten, bad voices," recalled Duncan. Hearing the overture, he turned to his wife, Gladys, and said, "It stinks." But before the next half hour passed, Duncan, mesmerized, was whispering that the score was "heavenly."

"Insular knowledge is just that, insular," says Duncan now, 44 years later. He laughs softly, speaking of those first encounters with Gershwin, without apology. "I thought I knew everything, I had my master's degree from Columbia University. I was comfortable in my own intellectual cocoon. I was naive but I was honest."

For decades now, Todd Duncan has been closely identified with the first role that brought him fame, the crippled beggar, Porgy. The folk'opera, as Gershwin called it, was seen by some critics - Ebony Magazine, for one - as a sterotype of black life, a minimizing of the richness of the southern black lifestyle, or, as Ebony once put it, a "'yas-suh-boss' portrait of colored life in Dixie." But it was a wild success, enjoyed several major revivals over the years, and this year even inspired a French fashion collection.

Its most famous character is still a part of the cultural scene. Today is Todd Duncan's 75th birthday, and in conversation he displays the same caution, bluntness, cool acceptance of fame, and gentility of the younger man. His publicity pictures from "Porgy" look down from the walls of his Washington studio, where he teaches voice, the eyes curious, the smile beckoning and the face flat, hinting at a Clark Gable-like glamor. Though his hair is snow-white now, the man sitting on th couch has not lost the arresting stature, and the lines in his face indicate a graceful transition to age.

Joking, praising and correcting, as she has done since their marriage in 1934 is Gladys Duncan, an effervescent and outspoken woman. In the 1950s she was a powerful politician in Washington, an officer in the Central Democratic Committee, the influential body in a city that was essentially voteless and still segregated. Her voice is still a respected one. The last two decades saw another Duncan emerge as a public figure - their son, Charles, formerly D.C. Corporation Counsel and Dean of the Howard University Law School where he now teaches.

Todd Duncan ranked with the most popular artists of his day. In the area that he liked best, the concerts, the most difficult vehicle for a black artist, he was successful, giving 2,000 recitals between 1940 and 1965. Like Marian Anderson and Paul Robeson, his contemporaries, Todd Duncan was a pioneer. In 1945 Duncan was the first black to sing a "white" role with a national opera company - the New York City Opera. He was the first black cncert artist to tour Australia.

When "Porgy" came to Washington, he insisted that the National Theatre be open to blacks, the first time ever. Because of the stir when the Duncans were refused a room in Caracas, Venezuela, in 1945, that country's constitution was amended to bar discrimination.

Besides Porgy, Duncan starred in two other Broadway shows, "Cabin in the Sky," with Ethel Waters, in 1940, one of the most successful black plays of the day, and in 1954, the Maxwell Anderson-Kurt Weill "Lost in the Stars." He made two films, "Syncopation," in 1942 an "Unchained" in 1955, but has turned down many others, he says, because they were demeaning.

His popularity was international. In a 1945 black newspaper poll, he was listed as doing as much for race relations as Ralph Bunche, the Nobel Peace Prize-winning diplomat; Jackie Robinson, the baseball player who broke the color barrier; Charles Houston, one of the lawyers who later worked on the case leading to the 1954 Supreme Court desegregation decision; and James Forrestal and Horal Ickes, members of the Roosevelt Cabinet.

Can there be a high point in all those years? Duncan puffs on his cigar, looks at his wife on the piano stool, pets their gray poodle, and takes a long time to answer. "I guess the night Toscanini came to the show, the New York City Opera. He came backstage, I was very flattered and excited. All he said was 'magnifico.' And I nodded, 'thank you.'"

The 17-year-old Todd Duncan was sitting in the "good seats" in the front center balcony of the then-segregated Brown Theater in Louisville, Ky. He was edgy, anxious for the concert to start. That night the great tenor, Roland Hayes, was appearing.

"I'll never forget any moment of that evening. A man came out and said Mr. Hayes wanted to apologize because his luggage had not arrived. So Hayes came out in his traveling clothes. It didn't matter. I just thought he was something of a god," says Duncan. He closes his eyes momentarily, thinking of the small, slender man, who was then in his early 30s, an artist who had to find his early fame in Europe, who was welcomed by European royalty while the doors of American concerts hails remained shut. Duncan starts to hum one of the songs, getting up and walking quickly to a book shelf. "Here it is," as he flips through a songbook. The song, "Benedict die sel'ge Mutter," is marked with a red cross.

About 20 years ago, the idol and the worshiper met. "I was singing at Boston's Symphony Hall, and I noticed a Negro man sitting up in the box. I said to my accompanist, 'Who is he?' and he said, 'Roland Hayes.' I remember fretting, 'Oh my God, why did he come here?' And when I went back out front to do my Schubert group, I couldn't think of the first three words. I made them up," says Duncan, a member of the generation that fought hard to be called Negro and still clings to that identification. "Hayes came backstage and I said 'You are the only singer in the world I am afraid of.' I had emulated him but never tried to compete with him.

"And he said "Whatever mantle I have, I pass on to you."

A number of years, however, passed between first seeing Hayes and taking his own steps on the concert stage. Todd Duncan was born in Danville, Ky., then moved to Indianapolis as a youngster, where his mother, Lettie, taught piano privately and his father, John, ran a garage. "Something like Fred Sanford," says Duncan, laughing loudly, "he had a garage, a car repair garage and a junk shop."

Young Todd started taking lessons from his mother when he was 5 years old.

He pursued music at Butler University, then taught at Simmons University in Louisville, and subsequently studied at Columbia University. In 1931 he was invited to join the faculty of Howard. "I had been contracted to teach at Wilberforce University when one of my teachers at Columbia said, 'We got this call from a school down south,' looking for a voice teacher. And he fumbled around, looking for a letter, and said, 'Oh, it was Howard.' Well, I thought that was like coming to heaven. I was from the Midwest. I knew all about the capstone of Negro education. We had studied Kelly Miller's book at school. I couldn't wait."

Once on campus, Duncan bacame pensive, hard-working and ambitious, taking time out for a tennis game, perhaps, but too shy to break into the intellectual circle of Miller, the educator, Lucy Dean Slowe, another famous educator, and Alain Locke, the first black Rhodes Scholar who was the intellectual force behind much of the black literary movement of the time. "I was just trying to get ahead," says Duncan, who left the faculty after he was discovered for "Porgy." Yet, his four years at Howard brought him many friendships that continue today - William Duncan Allen, a music teacher who was later Duncan's accompanist for 10 years, Dorothy Porter, the bibliographer whose late husband, James, the artist, also took voice lessons from him, and Charles Wesley, who taught history at Howard and later was president of Central State University, Ohio.

"Todd was always a serious, yet jovial person." says Wesley. "When I took my family to Europe for my Guggenheim year, Todd would write and keep us up on all the happenings. When we returned, he sang, "Since You Went Away,' based on a poem of James Weldon Johnson, at a party."

While at Howard, Duncan appeared in an all-black operatic program at New York's Mecca Temple. It was this perfomance that George Gershwin had seen and remembered.

"Porgy" opened in New York on Oct. 10, 1935. Duncan, then 32 years old, worked so hard he almost worked himself out of the role. "The first perfomance in the original almost killed me. I was a bundle of aches and pains and tortured muscles from crawling. But, in time, I learned to economize on my movements." Ever since it opened, arguments have swirled around "Porgy," and Duncan has chosen to argue its validity. "It was simply one facet of a Negro group, it was not the story of a dentist, a professor, it was the sory of a humble man. Porgy was a man with a brilliant mind and generous heart. It's one story," says Duncan. "Some of the black newspapers and some of my so-called friends at Howard called it demeaning. But I didn't."

While "Porgy" brought fame and made Duncan a lasting folklore symbol, he says it brought one of the low points of his career. He refused to play the National Theatre in Washington unless blacks were allowed. His union threatened to sue him for $10,000. "I couldn't bear to come to a theater where my own people couldn't come. So Anne Brown (the original Boss) and I sent letters to everybody, from Mrs. Eleanor Roosevelt down," says Duncan. "For two weeks, it affected my work on stage, my whole life. I had gone into social work and my artistry was suffering."

The National's management said Negroes could attend the matinee. Duncan said no. Then the management said Negroes could sit on one side of the theater. Duncan said not enough. Finally the theater was opened to everybody.

As he talks about the racial tensions of that particular incident, his voice snaps, his only real flash of anger of the afternoon. "But I won," he says. (It was years later - 1952 - before the National was fully integrated, only after a long boycott by patrons and actors alike, and an interval as a movie house.)

In the decade after "Porgy," Duncan appeared in London in the Edgar Wallace play about British colonialism in Africa, "The Sun Never Sets," then appeared on Broadway in "Cabin in the Sky," one of the few successful all-Negro musicals of the '30s. Some thought it was condescending. Duncan found his role unstimulating.

He was the "Lawd's General." But, as the stars were signed, especially Ethel Waters, recalls Duncan, the other parts diminished. "My part, as the good influence, with beautiful, classical singing, and Cab Calloway's role as the Devil, with his hi-de-ho, were cut. We became buffers, and Cab didn't do the show but I had signed for one year and did it."

Porgy was revived in 1942. Etta Motten-Barnett, who played the second "Bess" to Duncan's Porgy" recalls him fondly, especially praising his coaching of her voice. "But he was also moody, a typical artist, jovial at times, philosophical, happiest when performing, but not really outgoing," she recalls.

Says Duncan, "I was the same guy before and after my fame. I was only temperamental when I was not feeling secure in my craft. But in the last 25 years of my career, I was confident." Across the room, Gladys Duncan is squirming, as if trying to hold back a big secret. Later, she says, "When Todd was being temperamental, he would get an ailment. He would need orange juice or fresh pineapple juice. Once in London he had a cold and I had to go all over town looking for sour grapes. I got them for him, and he forgot to take them because, by then, he was totally at ease."

In 1945, the year his first movie, "Syncopation," was released, Duncan made what considered a breakthrough, singing the roles of Tonio from "Pagliacci," and Escamilio, from "Carmen," at the New York City Opera. It was the first time a black had played a lead role in a "white" production with a white company. The headlines screamed, "From Porgy to Pagliacci."

"My reaction was nothing," says Duncan. "The press was on my tail day and night, - 'How do you feel?' Well, we all had on greasepaint, what did it matter? I looked at it as an artistic step, not a sociological accomplishment."

Before World War 11, whenever the small circle of black concert artists - Duncan, Marian Anderson, Dorothy Maynor and Paul Robeson - would meet, they discussed the problems of racism. "We all share it, and we discussed the events with great regret, some anger and much frustration," recalls Duncan, who had a clause in every contract saying he wouldn't sing in a segregated hall.

"How could this happen? How could people feel that they could give you thousands of dollars for a performance, and you wouldn't be bitter about the way they treated your own people?"

But color was always an issue, whether color was establishing a precent or causing a ruckus. In 1945, the same year he was a soloist with the New York Philharmonic, Todd and Gladys Duncan were refused a room in a hoter in Caracas, Venezuela. Bill Allen, the accompanist, remembers a quiet, intense indignation from the singer. Gladys Duncan recalls, "We don't believe in ugliness, but our rights. Mr. D was shielded from a lot of those things on the concert tour. Yes, I protected and pampered hem. I only remember him being afraid once. He was doing "Porgy," in the South, and when he approached the front door, a policeman put a gun in his stomach, and asked him what he wanted." During the Duncan's second tour of Australia in 1949, a call came from New York to play the lead in "Lost in the Stars."

"There's nobody else," said Rouben Mamoulian, the director, "but Todd Duncan."

Though he was committed to two years of concerts, Duncan was not as subborn this time. He spent the night reading the script based on Alan Paton's "Cry, the Beloved Country," and then gave it to his Australian managers. "Can you say no to this?" he asked. "It's a role which has everything - bravery without rancor or ugliness - the kind of part I have been dreaming of since 1935."

Though the part has been criticized as just a change in stereotypes - from the shuffling black to the long-suffering one - Duncan found much of himself in the part. "He was a many-faceted man. He had love, faith, struggle, yes, hope in the pit of hell, as well as complete despair. I played it several ways, and saw something of Todd Duncan in that role."

"Washington is the only city where I am Gladys Duncan's husband," the singer once said.

So it happened that the Duncans fought for similar goals in different arenas. Twenty- five years ago, Gladys Duncan was the matriarch of the established black politics of the '50s and early '60s. She was president of the local chapter of the Americans for Democratic Action and vice chairman of the Democratic Central Committee, one of the few elected posts in the city at the time.

She drew her own battle lines. Fifteen years before District residents could vote in a presidential election, Gladys Duncan, a short, handsome woman, with marcelled curls, would walk the neighborhood around Georgia Avenue and Park Road, with Tilford (Ted) Dudley, a member of a patrician family with Mayflower antecedents. "We couldn't even vote in those days and people would wonder what are getting out of it," says Dudley.

They worked for national candidates. At the 1956 Democratic convention, she was the one who announced that the District delegates had decided to support Estes Kefauver, giving him the vice presidential nomination. In 1960 she was one of the District delegates who balked at the selection of Lyndon B. Johnson as the vice presidential candidate because of his poor civil rights record. At the 1964 convention, she fought for the seating of the Mississippi Freedom Democratic Party. "She backed me to the bitter end," says Joseph Rauh, who at the time was both counsel to the MFDP and delegate to the convention. "And the heat from the Atlantic City White House would have melted the Arctic. But Gladys never wavered an inch and we only got half of what we wanted." Gladys Duncan recalls, "What I am essentially is a truthful politician. I remember listening to both sides of the Mississippi delegation issue and then raising my hand and asking, 'Who is telling the truth?' A few people laughed but I was trying to make a point, and clarifying some of the superficial issues."

The Duncans met through the choir of the Plymouth Congregational Church, where Duncan served as a trustee foor many years. He was senior director of the choir and sang a special Easter Sunday concert. "Bill Allen suggested the choir get some lessons from Duncan. Both of them were at Howard. After one meeting, Mr. D. maneuvered so I would be the last out of the studio. And he said, 'Do you mind if I kiss you?' A year later we were married," recounts Gladys Duncan.

She was born in Charlottesville, Va., one of five children of school teacher parents. She came to Washington as a child to live with one of her sisters, then went to a private school in the South. She returned to Washington to study at Miners Teachers College.

Though their names were frequently in the paper and their magnificent home at 16th and T was the setting for grand partiess, the Duncans have never lost the quality their minister, Rev Theodore Ledbetter Sr., terms "humality."

When the politicians were meeting downstairs, Duncan was once discovered singing a lullaby to one of the guests' infant son. When a family friend's teen-aged son, named after Duncan, was seriously injured in a wrestling match, Gladys Duncan flew to Massachusetts to give blood. "Gladys is persuasive," says longtime friend Flaxie Pinkett, the political activist and realtor. "She even got me to sell scarves in Georgetown for Hubert Humphrey. She's a no-foolishness person. One Sunday we were addressing envelopes for something. I got tired before she did, but she wasn't about to stop until the job was done."

Even after the initial battles of home rule and desegregation were won locally, Gladys Duncan continued to be a strong voice, especially in the Rock Creek East Neighborhood. She kicked a nursing home out of the area, once fought against a service station - never mind that her son was representing the oil company. "The congressman at the hearing asked my mother if we were related, and she said, 'Yes, and I am very proud of him but right now I am bitterly opposed to his position.' The congressman said, 'Why don't you take him out to the woodshed and settle this?' We laughed about it later."

Only one cruel incident truly marred their personal lives, says Gladys Duncan: the killing of their daughter-in-law, Dorothy, five years ago. Todd Duncan, who remembers every detail of that day, says, "We haven't gotten over it yet. She was one of our joys."

Around the studio where Duncan has taught each day for the last 15 years are photographs of noted black singer Abbie Mitchell, conductor Artur Rodzinski, Alan Paton, Lyndon Johnson, Sara Lee, his first voice teacher, Hall Johnson, the arranger and composer, and William Grant Still, the composer. Photos of some of his many students, like George Fortune, now a success in Europe, and Philip Booth, with the Metropolitan Opera, also are displayed.

Since he retired in 1965, after singin at the Johnson inaugural, Duncan has been one of the principal voice teachers in the area. The rabbi's wife at the Washington Hebrew Congregation once sent a younger rabbi, with a high-pitched voice, to have lessons. Others have gone because of physical problems, such as improper breathing. For Todd Duncan, both his artistic and the socio-political roles, though small compared to his total career, merged when he was elected the first president of the Washington Performing Arts Society. It was, according to its members, the first local group to have large, integrated affairs. Over a Chinese luncheon in 1967, Patrick Hayes and Gladys Duncan, one of the seven original board members of the society, asked Duncan to be the first president.

"He said, 'Write it out for me, write out just what you want me to do,'" recalls Hayes. "It was very much the actor in him - 'I want to study the part; what are perameters?'"

Only once has he broken his retirement - to sing the role of "Job" at the Kennedy Center in 1972. What he has provided most seems to be inspiration. Some have found him naughty, but others, like television anchorman Max Robinson, have found him paternal. "I was at a very critical point in my career. And we were having a casual conversation and he said, 'Don't let them defeat you. We all have to fight and sometimes they will make you want to quit.' To me he was an institution, but he was just as interested in the dynamics of a life two generations removed from his," says Robinson.

Once in a while at a dinner or party Todd Duncan will get up and sing. At an awards banquet last year, Duncan told the audience, "I want to share with you what is in my heart," and he started singing, "Jacob's Ladder." One woman in the audience remembers thinking, "I want to die now because this must be heaven."