A FEW DAYS ago, a New York music critic put his finger right smack on the sorest problem facing opera houses and opera lovers these days: the growing shortage of first-rate singers.

A performance of "Tosca," which he called "a dreary affair," led the critic to this observation: "While the Met may have legitimate problems in casting the Italian war-horses, as they continually complain, surely they can do better than this!"

One of the things she singled out was the soprano -- "The bottom of the voice is weak; the soft singing is colorless; most of the loud singing sounded forced and unpleasant, and she phrases in notes, not in lines," (Yet this soprano, Carol Neblett, has been engaged for one of the Washington Opera's leading roles next season!)

As a result major opera houses are faced with compromising the product or withdrawing those operas from the market entirely for a while.

The problem is by no means confined to the Metropolitan. In an interview last summer, Carlo Maria Giulini talked about the difficulties in finding proper casting for many of the later Verdi operas. "Give me two casts for 'Don Carlo,'" he demanded. And he was offering the entire opera world of singers from which to choose.

Herbert von Karajan has been busy helping to spoil one of the loveliest lyric sopranos in the world by luring her into singing Elisabetta in "Don Carlo," and worse yet, "Aida"! These roles, plus a non-Karajan "Tosca" Mirella Freni recorded, have robbed her voice of its once-exquisite texture as well as its basic steadiness.

Yet Giulini's question will go away9 Does this mean that the world's major opera houses, including the Met and LaScala, must stop scheduling "Aida" because there is not a single great singer of the role anywhere in the world at the moment? There are, of course, sopranos who sing it. But not one who deserves to have her name added to that amazing list of sopranos who, over the past 50 years, sang the role with distinctive glory: Rosa Raisa and Claudio Muzio, Elisabeth Rethberg, Zinka Milanov, Eva Turner, Renata Tebaldi, Leontyne Price. The best the Met offers these days is decidedly second-rate alongside those memorable dramatic artists.

It is no wonder that Shirly Verrett is eager to take on the great part for Sarah Caldwell this spring, singing it with the Opera Company of Boston in that city and here at Wolf Trap.

From the evidence of her "Norma" here in 1976, Verrett should be a superb Aida. But notice that she is taking on the role in the closing years of her career, not in her early 30s -- which is the time when the greatest Aidas began to test the waters of the Nile. Price let it be known several years ago that she had "no intention of going down the Nile any more." The title role in Verdi's blockbuster is a demanding role for today's singers because most of them lack the basic control required for the long, arduous part.

Leaving the problem of why there is this shortage of spinto-dramatic sopranos for the moment, let's take a look at what happens when a Freni or a Scotto decides to move into the heaviest roles. Freni is, arguably, the best Italian soprano since Tebaldi. Neither Katia Ricciarelli nor Maria Chiara have fulfilled the hopes held for them early in their careers.

When she was here with the Paris Opera, singing her lovely Marguerite in "Faust," Freni told me, "I believe my voice is now developing to the point where I can handle larger roles than I have been singing." That belief, unfortunately, has led her, under Karajan's insistent guidance, to forcing bigger sounds from her voice than it sustains easily at its natural best. The whole problem lies in the false presumption that every voice, as its possessor matures, becomes capable of singing louder in larger and larger roles. Some do. Many do not.

Kristen Flagstad sang Mimi and Butterfly and Marguerite for most of her career before, at the age of 40, she moved into the Wagnerian repertoire in which she became immortal. Her voice grew. But Eleanor Steber went from one of the most radiantly beautiful Sophies in "Der Rosenkavalier" to the Marschallin where she was practically inaudible.

If the great Brazilian soprano, Bidy, Savao, had been a less intelligent singer and musician, she, too, might have followed the siren songs of opera managers and impresarios who wanted her to move from her exquisite Mimi, Manon, Susanna, Zerlina, Violetta and Melisande to Butterfly, Tosca and Elisabetta. She never considered these or other dangerous requests from any opera managements. And to her very last performance, no one ever called any part of her voice colorless, weak, forced or unpleasant. The same self-disciplines that ruled Sayao's career have preserved the voices of today's outstanding lyric tenors, Nicolai Gedda and Alfredo Kraus, both of them singing well into their 50s.

A little over a year and a half ago, Anthony Bliss, executive of the Metropolitan, released a statement concerning the company's financial well-being. "For the time in many years, the Metropolitan Open is undeniably on the road toward financial stability," he said. Then Bliss slipped badly: "The most important point of all," he added, "is the fact that the Metropolitan is now at a point of unparalleled artistic growth and strength."

That, as Bliss should know as well as anyone, is hogwash. The vocal sounds that have come out of radios on too many Saturday afternoons in recent seasons would shame many a far lesser house. More than once the only possible refuge from the constant display of bad singing has been to turn off the set.

This situation is by no means confined to the Metropolitan. It is endemic. Claudio Abbado, who resigned from his post as musical director of La Scala last fall has not resigned as conductor as well, severing every connection with the famous house in Milan. The situation in Italy's once-great music theater, compounded by a desperate shortage of money and an abundance of political maneuvering, threatens to wreck what has long been one of the world's greatest lyric houses. "Few people are willing to continue working there," Abbado said two weeks ago.

While Abbado was zeroing in on the political and financial troubles of the house, its secretary general, Fioravante Nanni, who left Scala for the Rome Opera last December, said, "Italian opera in general does not have a very high level of credibility right now." One of the reasons for that is the problem laid out by Giulini, the difficulty of finding relly adequate singers for roles once considered standard.

Perhaps, as James Levine mused a year or two ago, the Metropolitan Opera has actually reached the point where it cannot give "Aida" for lack of truly great sopranos.

This does not say that there are not, in the world today, some excellent sopranos. The New Zealand artist, Kiri Te Kanawa, the English Margaret Price, the United States' Catherine Malfitano, these are sopranos of high rank. But in the area of the big lyric or dramatic soprano, there is a shortage. We have excellent tenors for the Italian repertoire and good mezzos. But is it not better to shelve "Aida" and "Don Carlo" and "Forza" and "Turandot" than to hear the painful, often embarrassing attempts of those who are not equipped for these heroic roles? The thought of Caballe singing Turnandot at the Met next season is already sending shudders through any who know that opera properly.

Coming closer to home, as one who has advocated local performances of Motemezzi's "L'Amore dei Tre Re" for over 30 years, I suspect I would rather not hear it at all than to hear it with the soprano and tenor who have been announced for it next season.

The Wagnerian soprano scene is hardly more hopeful. Those from whom much had been hoped as singers of Isoldes and the Brunnhildes, Roberta Knie, Caterina Ligendza, Ute Vinzing, have not proven the answer. That Johanna Meier is now singing Isolde -- a role that Lotte Lehmann refused throughout her career, even when begged by Schalk and Walter to sing it for them -- means that Meier's attractive lyric voice is in danger. The idea of Hildegarde Behrens as Isolde is possible only because she will sing it with Berstein for the microphones of films and records.

We may very well be at a point where, for a time, certain areas of the repertoire will have to be held in abeyance until the next generation brings in new Italian and Wagnerian heroines. With plenty of early Verdi, plus his two masterworks still well castable, we should not suffer unduly. But it is a time for opera companies to stop mounting operas for which they do not have adequate singers.