"This is a maiden voyage," said Leontyne Price a few days ago. Her voice was not exactly nervous--a prima donna is never nervous, and Price seems to be totally without the fears that plague lesser mortals. But she was excited.

After 32 years on stage (beginning in 1951 with "Four Saints in Three Acts" and "Porgy and Bess"), Price was preparing for a new role: acting as host for a televised concert. Her debut as emcee was taped Sunday and will be telecast tonight on "In Performance at the White House" (Channel 26, 8 p.m.).

"I'm thrilled to have been invited by Mrs. Reagan for this occasion," said Price. But not thrilled speechless. She comes to the White House not only with a new job but with a message: "Why can't we have just a small soupc,on of the Yankee dollar put aside for the creative arts?"

"I have been in the East Room several times, now, and I repeat how thrilling it is to be asked by our first lady . . . It makes us as artists feel a part of everything. But we still have to take a tin cup, which I think we collectively resent. We are always so faithful and Johnny-on-the-spot when we are needed by our heads of state, or to represent our government and be ambassadors of good will.

"But if we could get funds from the government to maintain ourselves, that would really be the ultimate in showing how we are appreciated. We are the greatest country in the world, and we have the greatest arts and the greatest opera house in the world. Maybe we should take it a little more seriously from a financial point of view--legislate us into the budget, so to speak . . . It's not only the obvious solution, it's the easiest one by all means. Why not? It's done in Europe; it's done everywhere else. Why not in the most progressive, shall we say 'with-it' country in the world?"

For her television assignment, besides singing a Puccini aria and an ensemble from "Don Giovanni," Price will introduce six young singers from the Metropolitan Opera, which begins its 100th-anniversary season next week. The occasion brings out what she calls her "big-sister instincts": "I can think of no better way to start the Metropolitan's centennial year than presenting some of the wonderful artistic buds that they have under their wing--and to have someone hopefully fully bloomed like myself to sort of be mother hen at that occasion," she said.

She has just finished a long, luxurious vacation--working in her garden, a trip to Switzerland and a visit to Salzburg to watch some of her colleagues in action. She feels "glad to be back in harness" and is looking forward to the Met's centennial gala next month, when she will sing with "a colleague whom I have great respect for and who shares my initials--Luciano Pavarotti . . . in a duet--the duet--from 'Un Ballo in Maschera' by Giuseppe Verdi, who also happens to be a very good friend of mine."

The Met gala was organized after her 1983 fall tour had been arranged--it began last week in New Orleans--and required some tight scheduling--she flew off to Portland, Ore., the morning after the taping. This kind of rush is unusual at this point in her life, when Leontyne Price is usually exactly as busy as she wants to be. "I choose my own pace--isn't that what success is all about?--and that is how I am able to be starting the 32nd season of my career."

But she paces her rest as carefully as her work. "I am never relaxed or complacent," she said. "Resting on one's laurels is the most dangerous thing you can possibly do. The most wonderful thing about being an artist is the constant creating. It keeps you from being stagnant or bored . . . The technique is to take up the score again and approach it as if you have never seen it before, and there are always hidden things you have not discovered about a role."

Her two roles at the Met this season are Leonora in "La Forza del Destino" and the title role in "Aida," two of the most demanding challenges in the soprano repertoire. She had retired "Aida" from her repertoire a few years ago, but resurrected it on short notice last year to fill in for an ailing colleague in San Francisco. "The candle was lit again," she said, "so I think I will take another stab at it at the Metropolitan.

"Aida has represented so many things in my life," she said. "She has been a wonderful, personal part for me. And that is not for obvious reasons, either. She has had to say, as a character, whatever was happening to me at the moment, and I was always able to speak it through this part and say what I wanted to say. And happily, I think, some of the statements have been strong and meaningful."

This season may be the last time she sings "Aida." "After that," she said, "I think I will put it out to pasture and leave it for some of the younger ones." She paused. "Of course, I did say that once before . . . That's why I would never use the word 'retire.' I think any of my colleagues who have used it . . . I don't know if they really meant to use it, because they are so active still in so many different ways. With that kind of expertise, the experience alone, you will always be involved in something. I'm very fortunate because, thank God, I'm still active in a sense that I did not expect--and I'm not faking it. Well, no one in the business would let you fake it--certainly not audiences."

But while she is still busy as a performer, Leontyne Price is "experimenting with a new dimension" in her career: teaching. "My dear friend Maestro Von Karajan told me it would be a wonderful idea to do it while you can show young people what you are trying to do," she said. "He was quite right about that. I'm trying to start in the not-too-distant future to do some master classes. Sometimes that's difficult to do, because if you are active, managements like you to stay active. And why not? But I hope to combine the two."