IT WAS in December 1934 that George Gershwin first heard Todd Duncan sing.

A friend had told Gershwin about Duncan. The composer, who was finishing the score of "Porgy and Bess," wrote to DuBose Heyward, author of the book on which the opera is based, to say, "Here is an exciting piece of news: I heard about a man singer who teaches music in Washington and arranged to have him come and sing for me on Sunday several weeks ago. In my opinion, he is the closest ot a colored Lawrence Tibbett I have ever heard. He is about 6 feet tall and very well proportioned with a rich booming voice. . . . He is coming to sing for me again during Christmas week. I shall ask the [theater] Guild to take an option on her services."

This afternoon, Todd Duncan's matchless work as Porgy will be recalled when the Paul Hill Chorale, with soloists, offers scenes from the great Gershwin opera in the Kennedy Center. For Todd Duncan, who today still "teaches music in Washington," has been coaching the participants.

It was in the early weeks of 1936 that I first met Todd Duncan. He was in Chicago where the original "Porgy and Bess" company was touring with the show after its opening in Boston and New York the previous autumn. The pre-Broadway premiere had been in Boston on Sept. 30, and the New York City opening at the Alvin Theater was on Oct. 10. The road tour began in Philadelphia in late January, and on a cold night in February a bunch of music students from the University of Chicago went to the Loop to see and hear the new show.

Afterwards we were sitting in a Thompson's Restaurant -- the equivalent in those days of a Little Tavern or White Tower. We were clobbered by what we had just seen and heard. The company had included not only Duncan, who was far more than a parallel to Tibbett, but also Anne Brown, the slim and appealing Bess; Ruby Elzy, whose Serena had a heart-stopping quality; and Warren Coleman as Crown, whose entrance late in the picnic scene on Kittiwah Island was one of the terrifying moments in theatrical history. And there was the unforgettable Eva Jessye Choir. Above all, there was Gershwin -- in music none of us, in those days, had been able to anticipate from either "rhapsody in Blue" or the "American in Paris." We were in a state of post-curtain ferment as we went back over one great song after another.

While we were stretching out our poverty-level hamburgers and coffee, someone suddenly noticed a man sitting by himself over at a table by the wall."Was it?" we wondered for a moment, and then we were certain. It was Todd Duncan, the incredible man we had only a short time before been watching and listening to in the first great triumph of his career. His performance has always seemed, in the 45 years since "Porgy and Bess" first appeared, to be the greatest of all Porgys.

Somewhat hesitantly I went over and explained that we were from the music school of the University of Chicago, choked up trying to say how we felt about what we had just seen and heard, and timorously asked Duncan if he would come out the university some day during the run to talk with the students about the new opera. Gracious and generous as always, he instantly said he would be delighted to. The visit that followed was one of the most exciting afternoons for those who were lucky enough to be there to meet the extraordinary new star.

In the years since then only Duncan knows how many times and in how many countries he has sung "I Got Plenty of Nuthin'," or with how many sopranos his rich, elegantly-grained baritone has joined in "Bess, You Is My Woman Now." In hundreds of concerts and orchestral appearances, Duncan sang all over the world, his voice booming with a texture like burnished mahogany but also capable of subtle hints. Mingled with his gift for languages, that made him an admired recitalist.

It is the singular texture of his voice, along with certain insights into the character of Porgy, that have set Duncan apart from all his successors. Where some have lacked either the top notes or the lower range for the long and demanding role, Duncan's voice was smooth from top to bottom, with no hint of the breathiness or shortness of range that have impeded several of his well-known successors.

Gershwin had every intention of writing an opera when he went to work on "Porgy and Bess." It was not merely symbolic of that intention that he called it "Porgy and Bess," rather than simply "Porgy," like the Heyward book, so that he would be following in the path of "romeo and Juliet" and "Tristan and Isolde." But along with his hit tunes -- pointing out that "Carmen" is one long procession of hit tunes -- he also wrote solo scenes, duets and big ensemble scenes that demand voices of operatic caliber. Nothing proves better how completely he fulfilled his ambition than performances oof "Porgy and Bess" in which singers like Leontyne Price and Leona Mitchell demonstrate the real greatness of his writing. And it should always be remembered that the great songs are spread around the large cast: It is Clara who gets the first plum, "Summertime"; Serena who sings "My Man's Gone Now"; Jake who sings "A Woman Is a Sometime Thing"; and Sportin' Life the immortal "It Ain't Necessarily So."

Behind the purely vocal achievement, however, there was Todd Duncan's remarkable awareness of all the elements of Porgy's makeup, and the way that Gershwin's music illuminated the character. For instance, some baritones, inclluding Tibbett -- who joined with soprano Helen Jepson to record some of the most familiar scenes in the opera -- could not find the way to sing "I Got Plenty of Nuthin'" without resorting to a kind of declamation that is neither indicated in the score nor at all welcome from the stage. Duncan, like the greatest opera singers, was always able to realize the composer's intention by singing the notes as written. He also realized how touchingly human, with a gift for gentle humor and great tenderness, Porgy was at heart.

There was a memorable tenderness in the way Duncan took Bess into his little room when she was in trouble, giving no hint at all of the immense strength with which, when he had to, he would strangle Crown.

Because of his close friendship with Gershwin, his long and intimate association with the opera and his own musical insights, which have grown unceasingly in the years since those first Porgys, Todd Duncan's presence behind the scenes of this afternoon's performance in the Kennedy Center will give the music not only a nostalgic aroma but a kind of authority no one else could supply.

You can get an idea how Duncan will have been working with the Hill Chorale from this description he once gave of one great choral scene in "Porgy and Bess." Duncan said:

"One day we were in the midst of hard work on Serena's prayer scene. . . . This is a very quiet scene, one of profound religious fervor. We singers were very tired, tired enough fortunately to set up the exact atmosphere for the prayer. It must have been our 10th consecutive trial. . . . Miss Elzy [Serena] went down on her knees. Two seconds of silence intervened that seemed like hours, and presently there rose the most glorious tones and wails with accompanying amens and hallelujahs for our sick Bess that I ever hope to experience."

With luck, and Duncan's coaching, that's the kind of moment that might occur this afternoon.