IF EMPEROR NERO were alive today, he would probably want to be Mick Jagger. Nero, who fancied himself an artist until his dying day, committed suicide while insurgent forces were closing in on him after a military coup. His last words were "Qualis artifex pereo": "What an artist dies in me." At the height of his career, he had won a music competition in Greece, where the music competition and the artist-celebrity were invented, along with many other cornerstones of Western culture. No historian has ever hinted that the competition was unbiased.

Nero's instrument, incidentally, was not the proverbial fiddle (violins were not invented until around 1500 A.D.), but the cithara--a plucked string instrument whose name is related to both guitar and zither, but whose closest modern relative is the harp. Nero would have loved the idea of performing on television; he would have watched his Nielsens carefully and tried to rig the score or make it mandatory for everyone to view his shows.

Television is one factor that has escalated the music celebrity game to new heights in our time. It brings the performer into the home--millions of homes simultaneously--with an impact beyond the reach of radio or long-playing records. Not only do you get musical expression from Itzhak Perlman, you get his facial expressions at no extra cost. This heightens the experience and gives it a special sense of intimacy. Musicians like Perlman, Luciano Pavarotti and Beverly Sills become regular visitors in your living room, almost friends of the family. Their little mannerisms are familiar, and you know that they are the world's best because they are certified by PBS or even by American Express.

Certification of some kind is essential because most people (and Americans in particular) suffer from cultural insecurity. They look for a gilt-edged certificate of quality before they will commit themselves to wholehearted, spontaneous enjoyment of a performance. The result is an artificial widening of the gap between the superstars and those who are merely extremely good. Audiences who cannot tell the difference between one violinist and another will skip a performance by Henryk Szeryng or Sergiu Luca and flock to hear Perlman because he has the seal of approval. In this case, most of the time, they will get their money's worth because Perlman is an extraordinary artist. But when he is having a bad night (as he does occasionally), they will applaud just as loudly--for the performance, perhaps, but also for the celebrity status.

It may be useful to distinguish between musical celebrity and musical reputation, two phenomena that are related but not quite identical. Reputation is the respect of fellow musicians and expert music lovers, those who know the repertoire and analyze and compare performances. Celebrity is something larger but less significant. Mostly, it is recognition. Van Cliburn, Jean-Pierre Rampal and Renata Scotto are celebrities (along with Mstislav Rostropovich, Yehudi Menuhin, Vladimir Horowitz and others) because they are known to people who are not quite sure of the differences between a concerto and a sonata, or the similarities between an oboe and an English horn.

In classical music, reputation and celebrity are both based on performance. You simply do not attract attention in this highly competitive field unless you can perform at a certain level. Even Liberace is "a good pianist," I was recently told by an international star pianist (though not a celebrity) who won a Grand Prix du Disque for his recording of a Brahms concerto. Even critics who deplore a lot of the music James Galway plays will usually admit that he plays it beautifully--and when he performs serious music, he becomes a serious musician.

REPUTATION usually lags behind performance, on the way up and on the way down. It takes a while for the word to get around, unless you are booed into the headlines on an opening night at the Met. Menuhin burst upon the scene as a child prodigy at the age of 10, and for half a century he remained one of the world's top virtuosos. For several years now, his technique has not matched that of the average graduate of a good conservatory, but he continues to play to standing ovations.

Celebrity is even more erratic. Many musicians who deserve celebrity never really achieve it. Tenor Peter Schreier, for example, or oboist Heinz Holliger, or clarinetist Gervase de Peyer, none of whom you will see in American Express commercials this year. Or the members of the Chamber Music Society of Lincoln Center. Among connoisseurs, their reputations could hardly be higher, individually and collectively. But they do not sell out when they play at the Kennedy Center, as Cliburn, Pavarotti and Perlman routinely do. The reason is partly that their repertoire has less mass appeal, partly that they lack the extra touch of personality that escalates good music-making into celebrity status.

One traditional way of achieving both celebrity and reputation in a hurry is by winning a competition. But it isn't as easy as it used to be; there are so many competitions now, it is hard to keep the winners straight. Cliburn became famous overnight by winning the Tchaikovsky International Competition in 1958. His victory was not only a significant event in the ending of the Cold War; it ensured that for the rest of his life whenever he decides to sit down at a piano, the hall will be sold out.

His sudden rise to the top level of international stardom when he was only 24 years old also may have permanently stunted Cliburn's growth as an artist. He immediately became so busy showing people how he won the prize--that is, giving virtuoso performances of the top-40 romantic pieces for piano--that he had no time to develop new interests or fresh approaches to his favorite repertoire. Nearly a quarter-century later, he is still performing essentially the same music in essentially the same way. Some music lovers, watching the 13-year-old Greek prodigy Dimitris Sgouros begin what looks like a superstar career, may think of the Cliburn precedent and worry about the young pianist's future. Artistically if not financially, it is probably better to grow slowly.

That's what Rampal did. For years, he worked in orchestras and then began to make his name as a baroque flutist--a specialty that meant he was bucking the odds all the way--and he did it not only by superb musicianship but by careful calculation of his own abilities and audience tastes. There was an element of luck in his rise to stardom (there usually is), but he has used his luck wisely.

He came on the scene at a time when baroque music was just beginning to find a mass audience, thanks to the influence of long-playing, high-fidelity records--a medium that gave the solo flute a potential prominence hard to achieve in large, modern concert halls. Hampered by the relative scarcity of post-18th-century repertoire for the solo flute, he had music written for him by such composers as Poulenc and Jolivet. He has enlarged his audience with nonclassical recordings that range from Japanese folk melodies to the jazz suite composed for him by Claude Bolling, and he personally transcribed such pieces as the Franck Violin Sonata and the Khachaturian Violin Concerto for his instrument. On the evidence of his 60th birthday concert at the Kennedy Center this year, it may be time for him to stop playing the technically ferocious Khachaturian Concerto (which was only marginally worth playing at best), but in 18th-century repertoire his remarkable control of tone, phrasing and subtle shades of dynamics seems as impressive as ever. And he has diversified by branching out into teaching and conducting. Even in the face of severe competition from younger stars such as Galway and Paula Robison, he can be expected to stay in the spotlight for a while.

RENATA SCOTTO has the same basic problem as Rampal, but in a more acute form: Her stock in trade, like his, is the breath of life itself, and each passing year makes that breath a bit harder to produce and control. Like Rampal, she built her reputation slowly and solidly, singing for relatively small opera companies and recording relatively obscure operas for years before she became a celebrity.

The Met has been too slow in noticing several of the great sopranos of our time. Like Scotto, Beverly Sills had been a Metropolitan-caliber soprano for years before she sang there, and her voice was probably a bit past its peak when she made her Met debut. The opposite happened with Maria Callas; she auditioned for the Met in the mid-1940s when she was 18 years old and was offered a contract. She turned it down--the roles didn't appeal to her. Instead, she went off to Italy in 1947 and began to wow the audiences in provincial opera houses, beginning the long, hard road that brought her to La Scala in 1951 and back to the Met in triumph in 1956.

For Scotto, the reputation built so slowly and laboriously was almost completely destroyed in one evening last season, when she starred in a new production of "Norma," a role that is simply not good for her voice in its present condition. She seems headed for the same mistake next season, when she is scheduled to star in a new production of Verdi's "Macbeth." Backstage whispers at the Met say that she is obsessed with the memory of Callas, who also sang these roles and also had severe vocal problems. Callas had a stage magnetism that made hordes of fans willing to ignore the sometimes odd noises she made. Scotto is a good actress but has not quite inspired that kind of blind (or is it deaf?) enthusiasm.

Singers become celebrities more often than any other kind of musician, probably because their personalities are such an integral part of their performance. Most of the widely recognized names of musical celebrities from the past are those of singers: Caruso, McCormack, Melba, Patti, Melchior, etc. The only instrumentalists whose names have a comparable recognition factor today are probably Liszt and Paganini, whose fame is kept alive partly because they were also composers. In the long run, composers have an advantage over singers in the celebrity sweepstakes: Not many become celebrities in their lifetimes, but once established, their celebrity seems to last indefinitely. In contrast, the fame of singers usually lasts not much longer than the all-too-short span of their vocal prime. Today, only specialists recognize the name of Maria Malibran (1808-36), a contralto who was the Maria Callas of her time. Recording may change this situation for future singers, as it is already doing for some great voices of the recent past, such as Jussi Bjoerling and Leonard Warren. Meanwhile, vocal stars can console themselves by comparing paychecks with composers. A program is being worked out to place leading American composers in residence with leading American orchestras and to pay the composers a salary of $40,000 per year. Why $40,000? "We decided to pay the composers as much for a year as Pavarotti gets for one performance at the Met," was the not-for-attribution response. This price tag may go up. Horowitz allegedly received $60,000 for his recent recital at the Kennedy Center, and this is expected to have an inflationary effect on the fees charged by other superstars.

COMPOSERS who do achieve celebrity status while they are alive often lose it after death. While the Spohrs and Salieris are writing for their own time, the Mozarts and Beethovens have their eye on eternity. Beethoven was respected by his contemporaries, but most people (including virtuoso performers) found most of his music baffling. Mozart had the misfortune of being a child prodigy, both as pianist and as composer; in his lifetime (like Bach), he was more famous as a performer than as a composer, and his best music appealed largely to connoisseurs. Salieri was wildly popular at the height of his career but lived to see his fame wither. Now he is enjoying a very modest revival. Salieri compositions unheard for nearly two centuries are being performed and recorded because the composer is the villain in "Amadeus."

Is Aaron Copland the Salieri of our time? Ask again in 50 years; meanwhile, at least, in a long life he has not outlived his fame, and he has passed the 40th anniversary of some of his most popular compositions: "El Salon Mexico" (1936), "Billy the Kid" (1938), "Rodeo," "Lincoln Portrait" and "Fanfare for the Common Man" (all 1942). In sharp contrast, Gustav Mahler used to tell friends, "My time will come in 50 years," and he was right, give or take a decade; he died at 40 and would have had to live to be about 100 to enjoy the full benefits of celebrity.

Celebrity fastens itself on performers, who are in the public eye, and usually eludes composers, who are not. Take a second look at the living figures who could be called celebrity composers--Aaron Copland, Leonard Bernstein and perhaps Philip Glass--and they all turn out to be performers too. Copland reportedly decided to become a conductor after he learned that conductors were being paid more for performing his music than he had been paid to compose it. Bernstein (who is a better Copland conductor than Copland) is a triple-threat musical celebrity as composer, conductor and television personality--actually a quadruple threat if you consider his writing, but books like "The Joy of Music" and "The Unanswered Question" probably boost reputation more than celebrity. "West Side Story" is the stuff of which celebrities are made, particularly since it is the product of a composer with such impeccable classical credentials. It could be recognized eventually as Bernstein's masterpiece--a possibility which may or may not make him happy.

Among celebrity conductors, Mstislav Rostropovich is a special and fascinating case. For decades, he has enjoyed a reputation as the greatest cellist of his generation. His status gradually escalated to that of a celebrity--hastened by his warm and vivid personality, his association with Solzhenitsyn and the dramatic cancellation of his Soviet citizenship.

Now, as conductor of the National Symphony Orchestra, Rostropovich is exploring ways of sharing his charisma with 100 other musicians. His goal is to transform an orchestra that now hovers at the edge of America's top dozen into one of the world's best. It will take years to see whether he can do it, but the trend has been toward consistent improvement, in the orchestra's quality and his own performance as a conductor. Because he is Rostropovich, he has been able to take the orchestra on triumphal tours of three continents in the last two years and to bring the world's greatest soloists and guest conductors to perform here. The live telecast of an NSO concert to Europe last Thursday, with Bernstein and Michael Tilson Thomas conducting an all-Stravinsky program, was a fair sample of the kind of international prestige and exposure the orchestra is receiving in the Rostropovich era.

The Rostropovich share-the-charisma project is a fairly rare example of celebrity altruism: the use of musical prestige not merely as an end in itself but as a way to promote a worthy cause. Rare but not unprecedented; other examples are Perlman's use of his status to promote the cause of the physically disabled, the championing of American opera and particularly of young American singers by Beverly Sills, and the valiant, successful campaign waged by Isaac Stern to save Carnegie Hall from destruction.

More often, musical celebrity functions chiefly as a way to make money or to satisfy a hunger for power and adulation. A classic case history of the destructive power of celebrity status is the career of Maria Callas, who began an intensive quest for fame while she was still in grammar school--part of the Shirley Temple craze that was sweeping the world at that time. By the time she had made it, she had alienated her family and friends, terminated a marriage in which mutual exploitation seemed to be a major ingredient, and engaged in a variety of feuds that made international headlines. Eventually, her vocal problems became overwhelming, and she lost interest in singing. She staked her future happiness on the prospect of a marriage to Aristotle Onassis, who then dropped her and married Jacqueline Kennedy.

The most pathetic part of her career was its end; she tried to make a comeback via an international recital tour in partnership with tenor Giuseppe di Stefano. It was a fiasco, and she became nearly a recluse. It is a life that could be the subject of an opera. Perhaps Bernstein could compose the music, but who would dare to sing the title role?

On the whole, despite the Callas case, celebrities in classical music seem to have more orderly careers than their pop counterparts. The money at the peak is not quite as spectacular, but there seems to be more longevity, a gentler curve in the rising and falling trajectories. Could it be that, as he grows older, Mick Jagger will start wishing he were Luciano Pavarotti? Or perhaps the Emperor Nero?