Delete just one letter in the stanza's key word, however, and the 19th-century epic poem seems custom-made for the battle currently raging among American academics. There is canon all around them. And those who get involved in the fracas must feel as though they, too, are riding into the mouth of hell.

The heat was on, in any case, during a canon-oriented session titled '''New Emphases in Music History Teaching'' that figured significantly on the agenda for last weekend's meeting here of the College Music Society.

''Canon,'' in musical contexts, is an unfortunately ambiguous term. Its two very different meanings both derive from the Latin word for ''rule,'' but only one of them is in any way controversial.

The canon that is not at issue is a compositional device defined by its more or less strict adherence to a temporary rule - usually a rule involving some sort of melodic and rhythmic imitation - established by the composer. It's old-fashioned, to be sure, but no one has ever argued that, as a compositional tool, the canon does not work. The other canon, in contrast, is today being decried not just as old-fashioned but as completely unworkable, as artificial and irrelevant, as sexist and racist. At the same time, it is being adamantly defended, with rhetoric more powerful than it has had at its service in decades. This is the canon of Great Works, the body of certified masterpieces that - according to some unwritten judgment or ''rule'' handed down by posterity - are commonly regarded as the pillars of our civilization.

The panelists at the College Music Society session, naturally, chewed over the canon of musical Great Works. But the much larger canon of Great Works of all sorts has lately been the subject of similar debate.

A recent issue of Harper's magazine, for example, featured a symposium titled ''Who Needs the Great Works?'' The participants were asked to design a make-believe elementary school curriculum, a course of study that would give children a solid grounding in traditional Western culture while equipping them to deal with non-traditional, non-Western stimuli. It was not the specific content of ''the canon'' that was most contested. Rather, it was the very idea of canon. Some of the panelists argued passionately that certain works must be included by virtue of their exemplary greatness. Others argued, with equal passion, that the establishment of a canon - any canon - merely reinforces the cultural stereotypes that our society ought to be trying to eradicate. By setting up a canon, the iconoclasts said, works that don't fit the mold are automatically cast in a light that makes them seem less great, less worthy of attention and respect. They asked: Why not evaluate works of art on the basis of their unique merits or faults? Why not deal with works of art as they come, any which way, from whatever source?

The difficult position of ''the canon'' in our increasingly pluralistic nation was also raised by Charles Fowler in his new book ''Can We Rescue the Arts for America's Children?'' That children in the public schools should be taught to appreciate culture is not in question, Fowler said. But whose culture should they be taught? Their own ethnic culture, which might be anything from African to Amish to Lithuanian to Vietnamese? Or the mainstream culture of the United States, which remains firmly rooted in Anglo-Saxon, Judeo-Christian tradition? For school administrators, arts educators and politicians responsive to the voices of their minority constituents, this is a real problem.

Michael Beckerman, a musicologist at Washington University, opened the can of worms at the College Music Society session with a paper titled ''The Issue: The Musical Canon.'' Other examples of the debate, he said, are two of last year's best-selling books, E.D. Hirsch's ''Cultural Literacy: What Every American Needs to Know'' and Allan Bloom's ''The Closing of the American Mind'': Both - albeit in very different ways - argue for the necessity of re-establishing ''the canon'' as the anchor of American education. He mentioned, too, Richard Rorty's essay ''The Opening of the American Mind,'' which suggests that the argument hinges not so much on cultural artifacts per se as on the values contained within those artifacts.

''Talk of the canon is everywhere,'' Beckerman said. But why is it happening today, he asked. ''Weren't all these debates resolved in the '60s? Why now , in the laid-back, me-first '80s, has it all been revived?''

It's a good question. The answer remains elusive, but I suspect it hinges on something so simple as human nature. Back in the turbulent '60s, there was good reason to blast the canon.

In the first place, the canon was exclusive. The musical Great Works it encompassed were limited, by and large, to what Beckerman described as masterpieces by ''dead German composers.'' It certainly did not include popular music, music by American composers, music by women composers or music from non-Western cultures, all of which were discussed in turn by the other participants in the College Music Society's canon session.

Secondly, the canon had been exclusive for an irritatingly long time. Great societal changes took place in the '60s, the decade during which minorities of all sorts began standing up for their rights. Perhaps taking their cue from the various large-scale protest movements, scholars working in non-canonic fields demanded that their subjects, too, be granted places of honor in the halls of academe. They shouted loudly, and so did the many students who supported their efforts. All of this made a great deal of sense to the university administrators, who were not just liberal-minded but politically savvy. Little by little, the canon of Great Works - musical or otherwise - was disavowed.

That was in the stormy '60s. Now we are in the cool '80s, and we take it for granted that the ''Three B's,'' the ''Three M's'' and the ''Three S's'' (Bach, Beethoven and Brahms; Mozart, Mendelssohn and Mahler; Schubert, Schumann and Schoenberg) are not the only composers of merit, that at least some female composers are indeed the equals of their male counterparts, that at least some examples of popular music are every bit as artful as concert-hall fare, that at least some ''exotic'' musics are as sophisticated as music in the Western style. Not only do we know the value of this non-canonic music; we know the music itself, for the rapid growth of audio-visual communication in recent years has put practically all the world's music at our fingertips.

The same thing has happened in other areas of culture, in literature, film and the visual arts, certainly, but also in fashion and cuisine, in philosophy and psychology, in religion. That our horizons have been expanded is good. Yet it is precisely because of this expansion that the idea of a traditional canon is once again being championed. In a vast ocean of cultural stimuli, people need beacons if they are to feel something other than completely at sea.

Beckerman played the devil's advocate when, in his opening remarks, he challenged the need for a canon. But he took a different tack in his summary statement. He closed his first address on a sarcastic note, likening the musical canon to a ''set of porcelain busts on the piano, a canonized set of musical icons which, instead of encouraging a critical approach to thinking about music, merely represent yet another attempt to get students to assimilate supposedly venerated truths without question.'' Later, after the other panelists had had their say, he returned to the image of porcelain busts on the piano. This time, however, he represented them as elements in a kind of shrine, a place where an individual music-lover could worship and confirm faith in the Great Works of his or her choice. Without faith in something , Beckerman said, ''only limited questioning is possible. Without doubt, there is nothing but a primitive life of the mind.''

I couldn't agree more. Especially in a pluralistic culture, the need for personal identity is great. We can take in all that the world offers, and we can try to make sense of it. But we can never sort it out, to our intellectual satisfaction, unless we are able to compare it with a culture that we know is ours. Before we can appreciate what others might give us, we must first know who we are, where we come from, where we stand. We need self-knowledge; we need a canon.