In Bloomington, of course, no event can successfully compete for attention with a basketball game.

But opera on the Indiana University campus hardly goes unnoticed. Like the basketball team, the opera department of the IU School of Music traditionally ranks high in the polls. Talent is plentiful, and so are resources. After almost 20 years, the red, white and purple interior of the 1,400-seat Musical Arts Center still feels as modern as the Calder sculpture that decorates its front lawn.

Along with looking splendid, the facility is arguably the best-equipped, most acoustically congenial opera house in the country. The Big MAC, as locals call it, hosts between six and eight productions a year. Most of the shows sell out.

The IU production of Krzysztof Penderecki's "The Devils of Loudun" opened on Feb. 20, the same night the Hoosiers took to their home court to do battle with in-state rival Purdue. And it was only because of the game, said the folks at the MAC box office, that attendance was down slightly. Penderecki's opera, they said, had been the talk of the town for weeks, and tickets for the remaining performances were selling like hotcakes.

There was good reason for an excited turnout.

First of all, Penderecki is not just a good composer but an important composer, a world-class artist whose every work seems to demand an opinion from those who would be in the know. Secondly, although "The Devils of Loudun" has often been mounted in Europe, it had not had an American production since 1969. (The world premiere took place in Hamburg in June of that year; before the summer was over it was on the boards in Santa Fe.)

In terms of audience appeal, though, probably the most significant thing the opera has going for it is its sheer ghastliness.

"The Devils of Loudun" is based on a 1961 play by John Whiting that derived, in turn, from a 1952 novel by Aldous Huxley. Although the Huxley book is cast as fiction, its source material is a collection of eyewitness accounts pertaining to an execution that happened in the town of Loudun, France, early in the 17th century.

Maybe the devil really did stir it up in Loudun in the summer of 1634. According to the witnesses, however, the priest who was killed was not the devil's partner.

Father Grandier, to be sure, was guilty of many things: of arrogance, of womanizing, of intellectual superiority to those around him, of politics that flew in the face of the establishment. But none of these offenses warranted his horrible death.

Grandier was framed, the victim not so much of a mob but of a conspiracy. The culprits in Loudun were government officials and members of the clergy; it is largely from their writings that Huxley drew his facts, and most of these writings are blatantly confessional.

The trouble started, apparently, when the prioress of an Ursuline convent developed a crush on the very handsome Grandier.

When Grandier declined the prioress's invitation to serve as the convent's spiritual adviser, she grew obsessive. She went quite over the edge, actually, and when she came to her senses she made up an excuse for her lewd ravings. She had been violated by a devil, she said, by a devil who looked exactly like Grandier.

The situation that developed was one that a modern psychologist might call mass hysteria. For reasons that still seem baffling, the other nuns - one by one - claimed that they, too, had had sexual relations with a Grandier-like devil. Doctors and priests examined the nuns; they concluded that the entire convent was being just plain goofy.

To make a long story short, the nuns' strange behavior was made public precisely at the same time that Grandier's enemies decided they had had their fill of him. Accusations were made, charges were filed, a trial took place. The execution was attended by thousands of cheering people. Even with his dying breaths, Grandier swore his innocence.

Penderecki's opera dates from 1969. Two years later there was a movie version of the story, an adaptation by Ken Russell titled simply "The Devils." It starred Vanessa Redgrave and Oliver Reed, and the music was by the English composer Peter Maxwell Davies.

The film and the opera have more in common than just plot. Indeed, one of the most striking things about the Penderecki opera - aside from its music and its violence - is its pacing. As much as any opera created during the last quarter century, "The Devils of Loudun" seems modeled on cinema.

Its three acts are divided into 32 vignettes, and the performance time is just a bit over two hours. There are no extended arias or choruses. Although there is plenty of text, it is largely expository, not reflective, and most of it is declaimed in natural-sounding rhythms. The orchestra and chorus play important roles here, but usually they hover in the background, filling the scenes with vague yet potent "underscoring."

When the accompaniment is not being merely atmospheric, it is being concrete in the most shocking of ways.

Remember, the libretto that Penderecki himself wrote for "The Devils of Loudun" is filled with graphic detail. Act I is fairly mild, but Act II features both a fantasy orgy and an exorcism by enema, and Act II is taken up mostly with a step-by-step enactment of the torture and execution. Sustained moans pierced by sudden shrieks, explosive percussion followed by gurgling woodwinds, dense tone-clusters that swell up from the depths of the string section - all these are the operatic equivalents of Hollywood's special effects.

James Lucas directed the Bloomington production, and his staging probably was as realistic as community standards would allow. The cast was strong; vocally or dramatically, there was no holding back. Conductor Thomas Baldner was fully in command of the score.

As one would expect at IU, the production - with its scrims, projections, smoke machines and flickering lights - was state-of-the-art from top to bottom. And this made the music seem all the more dated. "The Devils of Loudun" sounds, as they say, very '60s.

The opera belongs to Penderecki's most outrageously avant-garde period. When he wrote it Penderecki was only 36, still fresh from a Poland that for decades had been under the thumb of Stalinist repression. Stalin died in 1953, and the artistic freedoms that Poland began to enjoy five years later were a cue - especially for young composers - to make up for lost time.

Penderecki burst on the scene like an enfant terrible. Practically everything he produced during the next dozen years resonated with bold gesture and harsh dissonance.

As deliberately cacophonic as much of it is, however, Penderecki's music from the 1960s is seldom without purpose and meaning.

The piece from 1960 that first brought him to international attention - and still is his most famous work - is titled "Threnody to the Victims of Hiroshima." For a few years after that he wrote music with abstract titles. But then, in 1965, came the vast "St. Luke Passion," and in 1967 the "Dies irae" that is a memorial to those who died as Auschwitz.

These are powerful compositions; they generate enthusiastic applause, but not before their message has been received in respectful silence. Whatever their subject matter, they have the effect of sacred music. They are dated in sonority, perhaps, but not in emotional or philosophical content.

Had he said those words a quarter of a century ago, no one would have believed him.

Today, however, allegiance to tradition seems so much a part of Polish composer Krzysztof Penderecki's mind-set that the only appropriate response to his statement is quiet affirmation.

He was once one of the most radical members of Europe's avant-garde community. But since the early 1970s, Penderecki has shunned the sweeping orchestral glissandos, the densely packed tone-clusters and other of the ''noise'' effects that first brought him to international attention in the years immediately following the end of Poland's post-World War II Stalinist regime.

Penderecki is not so much a convert as a born-again traditionalist, for his student works - composed several years before he burst onto the scene as a 27-year-old enfant terrible with his infamous 1960 ''Threnody to the Victims of Hiroshima'' - were quite in line with the conservative ideals he espouses today. Like persons born again to religion, he is absolutely steadfast in his beliefs.

Yet people have been wondering: Penderecki of course has his roots transplanted deeply into musical tradition, but with what section of that tradition does he now affiliate himself?

The question was raised in 1984 by the ''Polish Requiem,'' a large-scale work that showed strong signs of veering from the straight and narrow path of 19th-century-style tonality - almost in the manner of Brahms or Bruckner - along which Penderecki had been moving steadily for a dozen years. The answer - forceful and unambiguous - is contained in ''The Black Mask,'' a one-act opera that premiered at the Salzburg Festival in the summer of 1986 and currently is being given its first American production by the Santa Fe Opera.

If Penderecki was a neo-Romantic in such ear-pleasing works as the 1972 ''Violin Concerto,'' the 1979 ''Te Deum'' and the 1980 ''Symphony No. 2,'' then with this latest opera, he has surely become a neo-Expressionist.

Indeed, he did not object when, in an interview conducted two days after the July 30 opening performance in Santa Fe, the turbulent sounds of ''The Black Mask'' were likened to those of Richard Strauss' ''Salome'' and ''Elektra'' and - in its extreme moments - of Arnold Schoenberg's ''Erwartung.''

''You're quite right,'' he said, speaking in impeccable English. ''But I am not trying to imitate Strauss or Schoenberg; I have always written my own music, and this opera is no exception.

''Like those works you mentioned, 'The Black Mask' has nothing at all to do with tonality or with any other 'system' of musical organization. The harmony is extremely dissonant, yes, and the melodic lines are extremely angular. And, yes, it is intensely expressive.

''That puts it, I suppose, in the category of so-called Expressionist opera. In any case, it is very, very different from what I was doing just a few years ago.''

Why the change, I asked. ''Why does anything change?'' Penderecki asked back.

''In 1972, I needed to alter my style because I discovered that I had said all I wanted to say in my avant-garde language,'' he explained. ''Around 1983 or 1984, I discovered I no longer had anything to say in the tonal idiom, so I changed my style again. Perhaps in a few more years I will find yet another new style - although at the moment I don't know what that might be. For the time being, this is the style that for me feels most comfortable.''

Penderecki's first opera - spiced heavily with his trademark avant-garde sonorities - was the 1969 ''Devils of Loudon,'' an adaptation of the Aldous Huxley novel about alleged witchcraft and demonic possession in central Europe in the 17th century. His second work for the theater, commissioned by the Chicago Lyric Opera, was the 1978 ''Paradise Lost,'' a lushly orchestrated, unabashedly tonal treatment of the biblical story of creation as told in verse by the 17th-century English poet John Milton.

''The Black Mask'' is Penderecki's third opera. Based on the 1929 play of the same title by the German dramatist Gerhart Hauptmann, it, too, has a religious theme with ties to the 17th century. Its setting is the well-stocked but seriously troubled home of the Dutch-born mayor of a small town in the state of Silesia on the German-Polish border; the action takes place in the winter of 1662, shortly after the Thirty Years' War and on the eve of an epidemic of bubonic plague.

The Thirty Years' War was a struggle for political power and territory, but - like certain hostilities today - it wore the guise of a religious conflict. Although the Treaty of Westphalia had been in effect for almost a decade and a half by the time the scenario of ''The Black Mask'' unfolds, rivalry between Catholics and Protestants in the 1660s was largely unabated. The opera depicts an ecumenical gathering - the Calvinist mayor, his Catholic wife, their Huguenot and Jansenist servants, a Jewish merchant, a Lutheran clergyman, and so on - that only appears to be friendly; beneath the surface of pleasant chit-chat runs a stream of ugly hatreds.

This is the plot: The mayor's wife is being blackmailed by the former slave with whom she once had a liaison. Upon the arrival of the dreaded black man at the Silesian house (he's dressed, naturally, as a black masquer), almost everyone involved more or less suddenly falls victim to the plague known as the Black Death. The only survivors are the Jewish merchant, the black man and the illegitimate mulatto daughter born him long ago by the mayor's wife.

Clearly, the story is more symbolistic than logical. Michael Feingold, who provided the English translation for the Santa Fe production, writes in his program notes that the mayor's household and dinner guests represent the whole of European civilization in the 17th century; it is a civilization made wealthy by the practice of slavery, and for that crime against humanity it now must pay a severe but just penalty. (The stark symbolism of the characters and their demise did not prevent Viennese director Alfred Kirchner from coming up with a staging in Santa Fe that is for the most part realistic; Kirchner confuses the guilt-inducing issues, however, when he decorates the edges of the platform with enlarged modern photographs of starving children in Africa.)

Within the context of neo-Expressionism, Penderecki's treatment of this chilling parable is fairly straightforward.

Nothing remotely resembling an aria is heard in the course of the opera's 110 minutes, not even in the long soliloquy assigned to the mayor's half-crazed wife (stunningly portrayed by soprano Beverly Morgan) when she learns that her erstwhile paramour is on the premises.

Instead of lyricism, the audience gets earful after earful of conversational, or parlando-style, singing. But the speeches of this ''talky'' opera are charged with emotional inflections that boldly illuminate the characters who deliver them. And they are craftily overlayed, as are the elements of early Baroque hymnody and dance music, onomatopoetic sound effects and boiling Straussian orchestration that form the instrumental score. Many of the lines are incomprehensible because so many persons are jabbering simultaneously; when the texture lightens - as it invariably does every time someone puts aside his or her platitudes and attempts to communicate a significant idea - the effect is that of a bolt of light penetrating a thick, deathly gloom.

With a dozen corpses on stage - and two more up in the bedroom - at the finale, Penderecki's ''The Black Mask'' (which will be repeated in Santa Fe on Aug. 12 and 20) ranks as one of the grimmest new operas of recent years.

Perhaps it is for antidotal reasons that Penderecki's next theatrical work, scheduled for a 1991 premiere in Munich, will be an ''opera buffo'' setting of Jarry's ''Ubu roi.'' After that, Penderecki will turn again to serious matters; he has a commission from the Berlin Opera for a new work for 1992 or '93, but he has yet to decide whether the libretto will be based on Hauptmann's ''Magnus Garber'' (about the inquisition in 16th-century Germany), the Polish writer Stryjkowski's ''The Inn'' (about a pogrom in the World War I years) or Peter Schaffer's ''Amadeus.''

''I don't even know what style the opera for Berlin will be in,'' Penderecki said.