"Never enter a competition except to win. Some people say they enter just for the experience. Don't do that. It hurts too much. Anyone who can lose gracefully doesn't belong in this business."

THAT MESSAGE of cold, hard truth was delivered by 31-year-old virtuoso Santiago Rodriguez to a seminar of young pianists, their teachers and others who have staked their reputations, and their futures, on a grueling annual rite of musical hardball at the University of Maryland: the week-long International Piano Festival and Competition.

By then all but 15 of the 40 contestants had already been selected out with almost clinical precision by a panel of seven judges, sitting in the dark of the Tawes Theatre scoring each performance and whittling the array of musical talent down to a final three. The finalists, chosen late yesterday, were Alexander Kuzmin, an e'migre' from the Soviet Union, Remy Loumbrozo of France, and Liora Ziv-Li of Israel. The finals are tonight, and someone will win--unless there is a repeat of last year's contest, when no one was deemed worthy of first prize.

Rodriguez's blunt advice about this ruthless business carried real authority. For he is one of the very few who have risen to the top, surviving this Darwinian process by which the musical stars of the future are established--with all the glamor, adulation and wealth that go with such careers. Rodriguez won the Maryland Competition several years ago, and he sealed his chances for a concert career in 1981 at the Cliburn Competition in Fort Worth, where he dueled in a widely publicized bid for first prize with the better-known Andre-Michel Schub. He took a second, but with such a spectacular effort that no one thought of him as an also-ran.

At Fort Worth, Rodriguez, who is on the Maryland faculty, was in that classic now-or-never situation. "The Cliburn was the last competition of that magnitude that I would enter," he said at a seminar Tuesday. "The instant trap doors in which you are saved if you lose had run out. I couldn't have said, 'Oh well, there's always the Queen Elizabeth the celebrated Belgian competition in two more years.' I was 29 and I had a wife and child, and that had to be it."

Does that sound like the desperate Richard Dreyfuss character in that movie profile of such events, "The Competition"? Well, the biggest difference is that Dreyfuss' hopes were dashed, and Rodriguez's were not.

Anyone who thinks the arts are enclaves for innocent souls should witness one of these contests. A week of following the events and personalities in the Maryland contest--with performers pitted against pianists, pianists pitted against judges and sometimes even judges pitted against each other--suggests that the high drama of "The Competition" was not exaggerated.

Take the case of Howard Lubin, a 30-year-old pianist from New York who was one of the 15 to make the semifinals. On Tuesday afternoon at the Tawes Theatre he played a powerful version of the Liszt B-minor Sonata, one of the behemoths of romantic music. And he also played a Mozart sonata with style. The lay audience was much impressed, though one does not know how he went over with the judges.

He sounded like an artist with a great future. But in an interview, he sounded like Richard Dreyfuss in the movie--at his wit's end.

Lubin has been entering contests regularly since he was a star student at Oberlin 10 years ago ("I did very well at first"). But the big payoff that would launch a concert career has yet to come.

"I entered this one, frankly, as a lark," he said. "I think this is the last one I will do. I'm tired of earning no money as a solo pianist. If this one doesn't work for me, it's time to get off the merry-go-round. For awhile there I won pretty steadily. Then I entered a few more for which I was not very well prepared. But there were some thirds and second prizes last year. I might have stopped before now, but I have friends and teachers who make me keep going. But I'm not really hoping for anything. If I don't receive some overwhelming vote of confidence here I'm not playing anywhere." Meanwhile, he pursues an alternate career as a voice coach and accompanist in New York.

Lubin has pretty well isolated himself from the events in College Park ("I just don't care"). He is staying in a private home, as are the other contestants. The main requirement in these homes, located throughout the Washington area, is that there be private quarters and a good piano. Lubin is staying in McLean in a home that is very nice, but for the fact that the air conditioning failed, he said. "You wouldn't believe what it is like to practice the Liszt sonata in this heat," he mused.

Why does a pianist, or any other kind of soloist or singer, subject himself to this kind of regimen over a period of years? Rodriguez's answer: "We all live with the Van Cliburn syndrome. We all dream of the ultimate competition winner. We all suffer through that. We all dream that we will play so well that we will show any jury who we are." He refers, of course, to the most celebrated of all competition victories, the Cliburn victory in the 1958 Tchaikovsky competition in Moscow, where the young American's playing was simply so magnificent that he swept aside all the advantages then built in to protect Soviet contestants, won the gold medal, was embraced by Khrushchev and opened a new era in East-West cultural relations. (It is often forgotten that Cliburn had already won the Leventritt award, which is probably the most valued of American prizes).

Music competitions have been around for a long time. The Greeks held them. And a medieval vocal competition is the subject of Wagner's "Die Meistersinger." But competitions like the Maryland one or the Leventritt and the Tchaikovsky are products of the needs of the 20th century, with its geometric increases in both the supply of excellent musicians and in the size of the audience. There are, of course, great figures who never entered contests--Horowitz, the late Glenn Gould and both Rudolf and Peter Serkin. But they are the exceptions. Rodriguez observed, "Basically there are two ways to achieve concert careers--having friends in high places or winning contests." Ivan Moravec, the great Czech pianist, who is on the jury at Maryland, entered only one competition in his career, when he was very young, but he commented ruefully, "They have become a necessary evil."

Moravec worries about the arbitrariness of such a system. "The position of a juror is very complicated. It is not so hard when dealing with the top contestants or with the least. The trouble comes in the middle. They are the players with mixed qualities. You will hear Bach with the most beautiful timing and tone and style. And then the same performer will give you a Liszt Transcendental Etude that has no tone, no power. At first you hear something very sophisticated, and then you hear a dull, tired spirit. And it sounds like the person has emotionally and intellectually nothing to say. We find ourselves confronted with 15 separate combinations of strengths and weaknesses. And how do you decide what is important?" Part of the problem is, as Gary Graffman observes in his book "I Really Should Be Practicing," that "if all great artists were judged by what they play least well, nobody would be very good."

The judges score the players on a scale of 1 to 100. According to Stewart Gordon, who founded the festival and competition in 1971 and is now chairman of the university's music department, "The judges have an informal agreement that the more serious candidates will be scored in the range above 50." After each player finishes, the judges compute their scores and submit them to Gordon before the next player begins. "So far this year the judges have shown a high degree of agreement," he said.

That has not always been the case. Last year there was sharp disagreement on one finalist, and also a wrangle with Gordon about the decision not to give a first prize. Pianist and judge Lili Kraus, a venerable Mozart specialist, objected to Russian e'migre' Dmitry Feofanov's playing of Mozart in the finals, whereas the rest of the judges "rather liked it," recalled juror Paul Hume, former music critic of The Washington Post. Hume also recalled that Kraus disagreed about the playing of the Tchaikovsky First Concerto by American Michael Lewin, who had placed only a month before in the semifinals of the Tchaikovsky competition in Moscow. "We really expected him to make the biggest showing," Hume recalled. But among other things, he suffered some serious memory lapses in the Tchaikovsky. "So seven of us immediately agreed that there should be no first prize," said Hume. "Still Lili liked Lewin's bravura. We finally voted unanimously to give no first prize, and that made Stewart Gordon very angry. I thought he was going to keep us there all night until he got a first."

Gordon explained his position: "We have a contest every year, unlike the others, and I think we have a slightly different philosophy. We don't put these people in the public spotlight quite as much as some other contests do. In some of the others the person gets in the spotlight too early if he gets a first before his repertory is ready. But here we try to give contestants something else to come for besides to win, with the master classes and the concerts in the evenings." Then he added, "I remember some years ago there was a competition that declined to give a first so long that people began to wonder if they actually had the money." (The Maryland competition's first prize carries a $10,000 stipend, along with what Gordon describes as "modest" guaranteed concerts and recordings.)

The average age this year is higher than usual, with most contestants in their mid- to late-twenties. That's probably the reason for the general agreement that the level of talent is higher this year than last. The pianists were chosen from more than 100 applicants who sent in tapes of their playing.

But two of the semifinalists are quite young, 23-year-old Thomas Otten and 21-year-old Glenn Sales, and both are from the Washington area, which is unusual. It was the first try at an international contest by Otten, who graduated this spring from the University of Maryland. He was "thrilled" to make the semifinals. How about the finals? "I think I have a chance," he said. "It would be the icing on the cake."

Backstage gossip at a competition is about as discreet as it is at the Redskins' training camp or in the White House pressroom. A constant topic, for instance, was a new piece written for the competition by Mark Wilson, who is on the Maryland faculty. It is a short, atonal, minimal wisp of a piece called "Rituals," and the semifinalists all had to perform it. They accepted it like babies tolerate castor oil.

One contestant's reaction: "It was a disaster. I'll never try it again. The only time I played it all the way through was out there on stage in the semifinal round. And then I walked off stage and tore the paper in half. I wanted to take the two pieces back with me when I went back for a bow and wave them in each hand, but I didn't dare." His performance of "Rituals" was one of the better ones.

How much can a victory in the Maryland competition do for a young person's career? Probably it varies. Every competition has its strong years and its weak ones. But, in retrospect, this contest's potential was clear from its first year. Gordon recalled, "We only had about 25 applicants, and not all of them were that good. But we were lucky to have a few strong ones."

They were especially lucky in the little-known young man who took third. His name was Emanuel Ax. And today he has matured into, by common consent, one of the world's most distinguished pianists.