Ten days into his 86th year, Todd Duncan is still one of the most creatively busy men in Washington. Yesterday, as on every Monday, the great baritone was in his home on 16th Street NW teaching young singers who had come down from the Curtis Institute in Philadelphia.

"Make it passionate but not romantic -- it doesn't belong in that century," he told a young baritone who was singing a Bach aria. Duncan sat at the piano in the comfortable basement studio where he gives lessons every weekday morning, sometimes rippling out an introduction or accompaniment.

Gladys, Duncan's wife of 53 years, was busy elsewhere in the house while he gave his lessons, but stopped occasionally to enjoy the sound of her husband at work.

Photos stared down from three walls. The other was filled with a floor-to-ceiling mirror -- young singers have to pay attention to how they look, too. Some photos were of teachers, students, fellow musicians and Duncan's son Charles, who is an attorney and former corporation counsel of the District of Columbia. One showed the young, dashingly handsome Duncan of the 1930s and '40s, wearing a pencil-thin mustache and a smile almost as bright as the sunlight flooding the room -- the Todd Duncan who dazzled the world in 1935 as the first Porgy in Gershwin's "Porgy and Bess."

"He is about six feet tall and very well proportioned with a rich, booming voice," Gershwin wrote to his collaborator, playwright DuBose Heyward. "He would make a superb Crown and, I think, just as good a Porgy." That is the Todd Duncan who is most widely remembered today, but "Porgy" was only one highlight in a career that included opera and Broadway roles as well as more than 2,000 song recitals in 51 countries.

More than half a century after Gershwin's tribute, Duncan is still being honored, as he will be tonight at the John Wesley AME Zion Church. He still has a rich, almost booming voice -- perhaps not equal to what he once had, but better than his own modest description: "Not bad for 85 years old." He sings an occasional phrase for his students to show them how it is done, and the sound is firm, well nuanced, beautifully controlled -- a voice from which singers still in their twenties can learn much.

"I believe in putting the voice on the breath, not fooling around in the throat, and that is why I can continue to sing now," he says. "I sing every day with my students -- tenors, sopranos, baritones. If they can't do something, I show them how. My greatest joy is in teaching young people. I think that's why the good Lord is holding me here. That's when I come alive."

Asked how many students he has, he says, "Too many," then laughs and corrects himself. "No, I was just trying to be smart. But I have all the students I can take and I have a waiting list. There are always more waiting."

He is proud of "Porgy," of course, though he associates it with "aches and pains," since he had to spend the whole evening on his knees portraying a cripple, and he was originally reluctant to audition for Gershwin -- after all, he was a classical artist and Gershwin was a mere pop composer. "I didn't go the first time he asked me to audition for him," Duncan recalls. "I told him I was busy singing -- I had a little solo in my church, the Plymouth Congregation at the corner of 17th and P. It isn't there anymore." The second time, he did go to audition, he discovered that he liked the music, and the rest is history.

But besides recitals and teaching (which is perhaps his greatest contribution to the musical scene), that history includes "I Pagliacci" and "Cavalleria Rusticana" and a lot of musical theater not composed by Gershwin. "My favorite role was in 'Lost in the Stars,' " he says. Duncan was the singer for whom Kurt Weill tailored the role of Stephen Kumalo in his musical adaptation of "Cry, the Beloved Country."

As well as pioneering some of the great baritone roles in American musical theater, Duncan was one of the pioneers in the desegregation of the performing arts. Asked about his temporary integration of the National Theatre more than a half century ago, he says modestly that it has been "talked about too much."

"I just refused to sing there {in 'Porgy and Bess'} until they integrated, and they did," he says. But it was a step-by-step process with Duncan steadfast all the way. First the management offered to integrate matinees, and Duncan said no; then they offered to integrate one side but not the other, and again he refused until finally the theater was opened to everyone -- at least while Duncan was singing. After that, he had a clause inserted in his contracts stipulating that he would not sing in any segregated auditorium.

Back in his studio, Duncan is teaching a young soprano who shows a remarkable potential but a need for more work. Duncan is intensely involved in the music -- he treats it as a matter of technique and mystique, an intensely physical activity and a spiritual experience. He puts his hands on each side of her throat, showing her how to let the breath flow freely. "Go deep inside yourself and bring the music out from there," he commands. "Don't try to add things on from the outside."

The music is Hugo Wolf's "Herr, was tra gt der Boden hier," a meditation on Jesus Christ's death, and Duncan shows her how to treat it as a sort of prayer, not an operatic showpiece. Part of the lesson deals with different ways to sing the syllable "Ach!"

"This music doesn't need any circus tricks," he says. "Just let it come out in its own way and it will have its effect." He is totally involved; his eyes glow; he sings an occasional phrase sounding half his age. Music is this man's life; it has been since he began studying with his mother, a pianist, 80 years ago. When he is teaching, passing on what he has learned to tomorrow, it sounds as if the music -- and the man's influence, if not his still-vigorous life -- may go on forever.