CAN A CAREER be better the second time around? Tenor George Shirley thinks so. At 46 he relishes the idea of a repeat performance. And he will demonstrate what he means tonight in a concert at the University of Maryland.

"There's a sense of deja vu, going over old ground with new insights," says Shirley as he surveys the future from his studio at the University, where he is currently a visiting professor of music. "It's like starting all over again, like getting a second chance. I feel my best years are ahead of me."

That is no small prediction from a man with Shirley's past. In 1962 the right combination of talent and timing brought him into the Metropolitan Opera for a successful decade as its first black tenor. iAround the world he won roles -- Tamino in "The Magic Flute," Rodolfo in "La Boheme," Don Ottavio in "Don Giovanni," to name a few -- previously considered the exclusive domain of white tenors.

But in the mid-1970s a vocal crisis set in the Met contract was not renewed. Loss of voice, by Shirley's own estimate, was close to loss of self at that time. He cast about for help, considering everything from analysis to astrology, until he found his solution in Christian Science. f

Today he says the crisis is well behind him. He is a man clearly at peace with himself as an artist and a person. "I feel very, very good on both counts," he acknowledged. "I'm in a good place right now. I've particularly enjoyed the singing I've done during the last year. That's not to say there haven't been the usual bouts of being up and down. But I am gaining more consistency and I am pleased."

The major force behind the change, according to Shirley, has been mental. "Singers get so wound up in themselves," he explained. "You start thinking of yourself as a throat with legs."

"I know now that I'm more than a singer. I'm able to see the other parts of myself -- as a family man, a husband, as a parent, a teacher. I'm more of a human being than a singing machine.

"In the past, singing was an ego trip," he continued. "There was the big 'I,' reaping all the benefits. If something went really well I wanted to know how I could repeat it, how I could control it."

Yet even as he was trying to exert complete control over his art, Shirley notes, the best performances were frequently those in which he seemed to have no power over what happened.

Gradually, Shirley began to find his artistic and personal answer in a form of surrender -- an attitude reinforced by Christian Science teachings, which he turned to on a friend's advice a year and a half ago. "We had a saying in the black church that I grew up in -- 'Let go and let God,'" explained Shirley. "I work now to try to clear all false sense of ego out of the way, the idea that I'm responsible for bringing anything about, whether it's an insight to a student or a good performance. I don't have that power. That was the old way of thinking."

Without embarrassment he goes on to describe his own spiritual struggle -- a rare combat, as he points out, in this matierially oriented age. "It was extremely difficult to acknowledge that I exist to be used as a tool for the ends of God. Nobody wants to be used as a tool for anything, but I forced myself to say it over and over again. Now it gives me tremendous pleasure. It also takes a great load off my shoulders and enables me to do the best I can with the talent I've been given."

In Shirley's view his voice is returning to an earlier richness that was lost when he tried to force a certain sound quality. He finds a better flow in his performances, a judgment he sees confirmed in the positive reception given to his appearances within the last year and a half.

He is looking forward to the recreation of one of his favorite roles this summer when he will sing the lead in Mozart's "Idomenio" with Benita Valente at the Ottawa Festival. In December he will be singing with Julius Rudel and the Buffalo Philharmonic, an opera he first sang as a student at Wayne State, Stravinsky's "Oedipus Rex." He finds the prospect exciting even though he has performed the work under many conductors, including the composer.

Tonight's benefit concert at 8:15 in the University of Maryland's Tawes Recital Hall will include the world premiere of "Second Voyage," a composition for tape and voice written for Shirley by the American composer James Dashow.

For this evening, as for all his performances these days, Shirley has a simply stated philosophy. "You do your work and then you go out there on the stage and you trust. You let go. There's nothing you can hang on to if the performance is really going to soar."