The most frequent question asked of a music critic usually goes something like this: "What do you see as your role?" And, running neck and neck: "For whom do you write in YOUR paper?" as if the answer might be different in Akron than in Chicago.

These are good and basic questions for any critic. From time to time, especially when there is a new regime in Washington, the critic should check his answers to see if anything has charged since the last time.

The critic also must keep in mind the answer to one more question - and it usually comes just before or after those two. "What do you have to know to be a good music critic?"

Virgil Thomson, the American composer who was for some years also the country's finest music critic, writing for The Herald Tribune in New York, gave the definitive answer during a three-day conference on music criticism at Harvard 30 years ago. He told the large gathering of practicing music critics, "You have to know everything about music - and how to write." Later he added these vital requirements: "A critic must have real warmth he must have truth, and he must stick his neck out."

Aaron Copland, writing in "Copland on Music," adds a dimension to music criticism that some other musicians choose to overlook. Copland said, "A critic is not just a detached bystander whose job may be considered finished when he has given the composer a casual hearing. No, a critic is just as much a member of our musical civilization when he writes his criticism as a composer is when he writes his music."

That does not simplify the job, does it? Thomson says the critic is expected to know everything, and Copland rightly places him solidly inside the musical hierarchy. Having established the criteria, let's get down to the perpetual paradox: The critic has, for his tools, words with which to write about an art which is in itself a self-sufficient language.

His job is to tell his readers what is going on in the world of music, to be for them a mirror of that world - what he has heard and how it sounded. It is not his job to teach singing or how to play the violin or the piano or how to conduct an orchestra or how to compose, though it does not hurt in the least if he knows how to do any number of these. Nor is it his job to act as press agent for any concert management, performing arts center or artist.

The critic's newspaper expects him to keep its editors informed about the major events and trends in the entire music world and to give its readers an informed opinion about those events and trends. That matter of opinion causes the most commotion. Probably the fact most reqularly forgotten by newspaper readers, especially when they disagree with a review, is that the critic is expressing just one man's opinion - his own.

That opinion is presumed to be based on intensive and continuing study of many aspects of music - all aspects of the kinds of music the reviewer covers. But it is, obviously, only his opinion.

That fact is the best and simplest reason why two critics may go to the same concert and differ about what they heard. At the average National Symphony concert these days there are 2,800 listeners, On any regular night, you might very easily get at least a hundred, if not 2,800 different opinions about what went on there during that concert. Among musicians, howerver, there is not likely to be a substantial difference of opinion on basic elements of a concert. This means that, as a rule, two critics will agree about a singer's intonation, or whether a pianist forgot something in the middle of a Chopin Ballade.

But the whole subjective realm of how a performance sounds to two different pairs of ears opens up such differing views from critics as "The conductor was faithfull to Brahms' markings so that the Second Symphony came out entirely in the spirit of the score" or: "The departures from what Brahms marked in the score reached such proportions that the spirit of the work was seriously marred." What does the reader do then? He says his money and takes his choice.

It is not so much a matter of who is right, or of right at all. It is more a matter of which critic you know well enough to decide for yourself from what he writes just what went on in that concert. As Copland noted, the critic should be as serious in his study of the music involved as the composer has been in writing it. This is as true when the critic is going to a standard program of Bach. Beethoven, and Bruckner as it is when he is going to hear th first performance of a new work by David Del Tredici.

An essential element of the good critic is an intelligent mixture of enthusiasm and plain old-fashioned love of music. Surely that is what Schumann meant by "a warm heart," what Thomson had in mind when he said the critic needs "warmth." The moment a critic stops loving music, he should retire. If he cannot be aroused by great performances of the final pages of the "Meistersinger" Prelude or Debussy's "La chevelure," by a pianist triumphing in "Gaspard de la nuit," or an organist doing wonders in the G Minor Fantasy and Fugue of Bach, or Messiaen's "Dieu parmi nous," if he is not ready for the great frenzy that opens Verdi's "Otello," then he has no business writing about music.

Because one of the critic's greatest responsibilities and greatest privileges is his power to convey to his readers something of that unique beauty, that rapture that music alone among all the arts can produce. It is as much his responsibility to awaken these feeling in his readers as it is his duty to say frankly when performances fail to reach heights he knows are attainable.

Among the hazards against which the critic must guard both himself, and, he hopes, the public, is the easy acceptance of the Lowest Common Denominator in standards. The instantaneous standing ovation has, of late, become as much a method of routine applause as the universal use of the label "maestro," which once implied a very special mastership. The public is often willing to rest comfortably in the face of the hundredth playing of the most familiar music. And, for what may ee psychologically fascinating reasons, the public is often afraid of that which is new and unfamiliar.

One of the most useful things a critic can do is to try ahead of time to help the public understand some new music that is coming to performance in the near future. A few string quartet with electronic tape by Leon Kirchner, or the first hearing of "Makrokosmos" by George Crumb, or the Washington premiere of Alberto Ginastera's new opera, or the first hearing of David Del Tredici's "Final Alice" can be made an adventure in the world of the unfamiliar if the critic will write before the concert in a way that will give the listeners some clue about the way the composer does what it is that he does.

Contrary to what many people think, critics are not always arguing for more and more new music. Critics are far more likely to be urging performers in every area of music to revive works that have been unjustly neglected, to look into segments of repertoire which the critic may think the public would love if it only had a chance to hear them. He is frequently more interested in the second and subsequent peformances of fine new works than in their premieres. But any good critic will certainly argue that any new composition that a performer has decided its worth his time and effort to master deserves the courtesy of at least one full hearing.

The critic has another responsibility which the nonwriting listener does not have: The critic must remember not only the younger composer who may be enjoying a premiere, but also composers who are now in their 50s and 60s who were once the favorites of performers but who have more recently been proclaimed "on the shelf" or "old-fashioned" by arbitrary snobs. The dangers that insistence on first performances brings on are at least as damaging to the cause of musical progress as the ignoring of new young talents.

The music critic, in other words, must do all he can help his readers to love music as he himself does.