Opera concerts used to be a regular feature of the concert agenda of any important musically oriented metropolis. The tradition lives on in places like Vienna. The closest the United States has come is the Luciano Pavarotti outings at Madison Square Garden (one of which was telecast in August on PBS).
Operas in concert are a relatively recent phenomenon, a convenient way of encountering works that have either been forgotten or have fallen out of favor. This forum has recently afforded the chance to hear Rossini's ''William Tell'' and Glinka's ''A Life for the Tsar,'' thanks to the enterprising Eve Queler and her Opera Orchestra of New York. This past Sunday, Handel's ''Orlando'' served as a kickoff to the four-installment Handel Opera Festival. Until the early '70s , Gluck's ''Orfeo ed Euridice'' used to be a staple at the Met, and in October the Philadelphia Orchestra brought the opera to Carnegie Hall to allow for a now infrequent - but welcome - encounter.
Clearly, operas in concert serve a purpose, filling a void, particularly when the seriousness of the intent is amply on view. In the case of the Philadelphia ''Orfeo,'' seriousness was paramount, almost drowning the work in it. In ''Orlando,'' the Handel Festival offered name singers in suitable repertoire under an assured conductor's watchful care. In comparison, Miss Queler - although she could hardly be called frivolous - somehow lets her presentations go on without the polish that would make them memorable rather than serviceable.
What else determines success in this genre? Well, there is the question of the version used in each work. So many famous operas were revised by composers, and interest these days has focused on first versions. In other instances the standard performing version is encrusted with inserted arias, scenes, key transpositions, and other changes that have become part of the standard printed score.
Handel operas have suffered alterations throughout their history, but the edition used in the 31/2-hour festival performance was said to be authentically Handelian. Gluck wrote ''Orfeo'' for Vienna, then rewrote it for Paris. Traditionally, the best of both versions has been pasted together to make a satisfying operatic encounter. Riccardo Muti chose to return to the unadorned Vienna edition, which drops the celebrated ''Dance of the Furies,'' as well as a lovely aria for Euridice (who becomes nearly a bit player here) and a virtuoso aria for the hero.
Miss Queler, for some peculiar - and, finally, indefensible - reason chose to perform the sanitized Soviet version of the Glinka opera, which deletes all reference to the old regime - the czars, the Russian Orthodox Church, etc., etc. , and renames the work ''Ivan Susanin.'' This seminal work in the history of Russian opera suddenly becomes a trivial tale of a man who gives his life for the general good of proto-Soviet mankind in czarist times. With the Rossini work , written for the Paris Opera, Miss Queler opted for the Italian version (though the work is clearly, gloriously French grand opera), which is cut so brutally as to be little more than the Reader's Digest Condensed Book version of the massive work.
Without a uniformly good cast, no opera can really bewitch, in an opera house or on the concert stage. Mr. Muti offered Agnes Baltsa as Orfeo - an often electrifying mezzo who may lack the ultimate richness and depth of timbre to be ideal in the part, but offers more temperament than most in the role today. The Amore of Arleen Auger was lovely to the ear, but the Euridice of Margaret Marshall was neither vocally appealing nor histrionically ingratiating.
Marilyn Horne, the raison d'etre for ''Orlando,'' gave a spectacular account of the role - rich in tone, seamless of line, accurate and dazzling in the coloratura, constantly aware of words, mood, and vocal color. In fact, she was the only singer to project the work as opera: Everyone else was in oratorio land. Singing ranged from the shrill, colorless soprano of Valerie Masterson (Angelica) in this performance to the tasteful countertenor of Jeffrey Gall (Medoro). The lovely timbre of Marvis Martin's lyric soprano is still in need of serious fine-tuning before she will really be ready for so challenging a role as Dorinda. And Robert Lloyd's sonorous bass filled the hall effortlessly, although he seemed misplaced in the role of Zoroastro.
''William Tell'' was sung by Italian baritone Piero Cappuccilli, a sadly infrequent visitor to this city. His general dramatic aloofness gave way, in his aria ''Resta immobile,'' to such full-bodied, passionate singing that it had to be encored. Tenor Franco Bonisolli has the right sound for the grueling role of Aroldo, but he was out of voice for the dizzying number of high ''B's'' and ''C's'' that pepper the role. Stefka Evstatieva's pretty-voiced (except under pressure) but bland Mathilde and Kevin Langan's tentative Farst completed the principal cast. The supporting singers were all startlingly inferior.
In Miss Queler's Glinka outing, Martti Talvela failed to bring the towering role of Susanin to life, while the rest of the uneven cast struggled aimlessly with a work that needed stronger guidance from the podium.
Here, then, is where operas in concert rise or fall: When the conductor is truly in command - can truly marshal the forces into something rousing, confident, blazing - an impressive evening is possible. Nothing less than that was demanded in both ''William Tell'' and ''A Life for the Tzar,'' and Miss Queler was found wanting on both occasions. Something more than sacred oratorio was needed in the Gluck, and - no matter how beautiful it was to listen to under Muti with the Philadelphia Orchestra and the Westminster Choir - this ''Orfeo'' was never convincing as opera. Nor did ''Orlando,'' because Sir Charles Mackerras was more intent on orchestral detail, and musical proportion, than on the vitality and bewitching variety of tempos, moods, and orchestral timbres needed to bring Handel to life - despite having the finest orchestra this festival series has ever had: the Orchestra of St. Luke's.
Miss Queler closes her season April 14 with Lalo's rousing rarity ''Le Roi d'Ys.'' The Handel Festival continues with ''Ariodante'' (Tatiana Troyanos in the title role) Jan. 27; ''Semele'' (Miss Horne, Kathleen Battle, Rockwell Blake , Samuel Ramey) Feb. 23; and ''Alessandro'' April 28.