The Metropolitan Opera is bringing Wolf Trap some of its finest repertoire and artists this week. In contrast to past years when operas, singers and productions were from hunger, this week offers, in order, "Tosca," "Don Pasquale," "Otello," "Dialogues of the Carmelites," "Don Carlo" and "The Bartered Bride."

James Levine, the Met's music director, will make his initial Wolf Trap appearances, taking charge of the "Otello," "Don Carlo" and "Bartered Bride." James Conlon, who has been in charge of "Tosca" in New York City this season, will lead it to open the week on Monday. Nicola Rescigno, who led a notable account of Bellini's "I Capuleti e I Montecchi" for the Washington Opera recently, will be on hand for the "Don Pasquale" on Tuesday, and Richard Woitach will conduct the "Carmelites" on Thursday.

There have been the inevitable cast changes from some of the first-string singers heard during the Met's past season. But a week in which Jon Vickers sings Otello and then turns comedian for Smetana's Vasek is notable in any opera house. Nicolai Gedda will sing in both "Don Pasquale" and the "Bartered Bride," and the Romanian tenor, Vasile Moldoveanu is the opening night Cavaradossi, with Leonie Rysanek, who is still vividly remembered for her Tosca with the Deutsche Opera two years ago in the Kennedy Center repeating that role.

While "Otello" is probably the greatest masterpiece of the week, this is a rare occasion to discuss both Francis Poulenc's finest work "Dialogues of the Carmelites," and Verdi's "Don Carlo," which holds a very special position among his strong middle operas.

Nothing Francis Poulenc wrote gave him greater pain in its creation, or greater joy when he had finished it, than "Carmelites." The pain came, after the opera had been commissioned by the publishing house of Ricordi in Milan, because of conflicting rights over the literary sources of the opera.

The title page carries this unusually detailed pedigree: "Dialogues of the Carmelites, an opera in three acts and twelve scenes, text from the play of Georges Bernanos, produced at the opera with the authorization of Emmet Lavery. This play was inspired by a novelette by Gertrude von Le Fort, and by a scenario by Philippe Agostini and the Reverend V. Bruckberger."

In 1954, when Poulenc had been at work on the new opera for some months, serious difficulties over the ownership of the various sources were raised.

At the end of that year, Poulenc wrote his close friend, Marthe Bosredon, "Have been in such a state of nerves the I had to cut short my engagements in Germany after two concerts and enter a sanitorium." It was only after months of difficult negotiations that the legalities were cleared up and Poulenc could resume work on an opera whose characters had become vivid and dear to him.

He described them and their voices in a letter to his inseparable friend and greatest interpretor, Pierre Bernac: "Naturally it is necessary to write [the role of Mere Marie] for a mezzo, and to give Sister Constance to a light soprano, the second prioress to a "grand, [big lyric] soprano." The voice for Sister Blanche was never for a moment in queston. From the moment of conceiving the part, Poulenc knew it would be sung in Paris by his incomparable soprano, Denise Duval.

This did not prevent him later, however, from speaking of Rosanna Carteri, who created the role in its world premiere at La Scala on Jan. 26, 1957, as "prodigious." Within a year of that premiere, the "Carmelities" was being sung in Vienna, Cologne, Naples, Geneva, Rome, Lisbon and the United States, including a performance on NBC televised opera.

The story of the opera is taken from an actual incident of the French revolution, when an entire community of Carmelite nuns was guillotined. The "last on the scaffold," as Emmet Lavery's version was called in English, refers to Sister Blanche, a member of the aristocratic family of La Force, who joins the Carmelite order in a "quest for a life that is heroic," and whose struggle for courage finally leads her to the guillotine.

Drawing on Blanche's father and brother, as well as the chaplain of the Carmelites, a jailer a doctor and several revolutionary officials, Poulenc adds enough men's voices to his score to provide the balance needed in an opera dominated by the women who are at its heart. His gift for lyric writing, which made his songs the most beautifully written between 1918 and 1960, is mirrored in the superb, radiant vocal writing that marks every page of his opera, as well as in the orchestral accompaniment, which is flawlessly matched to the dramatic situation.

The final scene, on the Place de la Revolution, is one of the most theatrically dramatic, effective and heart-stopping in all opera. Known to those who by now know and love the opera, it should not be given away to those to whom it is still unknown.

The Metropolitan has cast the "Carmelites" strongly in most roles. The presence of Regine Crespin, who sang Mme. Lidoine, the second prioress, at the Paris premiere int eh summer of 1957, is a stroke of fortune. Her enactment of the old prioress is a masterpiece.Maria Ewing, while appealing as Sister Blanche, is a mezzo, in spite of Poulenc's express direcions concerning the voice. But the world is a bit short of Duval-type lyrics at the moment. Woitach's conducting of the opera is an unknown quantity. Michel Plasson conducted it at the Met two years ago when the work first entered the repertoire. He was far more affecting in it at that time than he was this year in the broadcast. Perhaps Woitach will touch all the right notes.

Several things are of central importance in speaking of Verdi's "Don Carlo." First of all, never before has the Metropolitan given the whole opera without cuts. Verdi wrote it originally in French and wrote a far longer opera than most opera houses wanted to present. He himself made various cuts at different times, including the entire First Act. At alst, the Met is presenting the entire score, though a detailed account of just how it has been put together would take more space than is available at this moment.

For the record, the 8 p.m. curtain means that "Don Carlo" will not end until approximately 12:45 a.m. Pick your baby-sitters accordingly.

"Don Carlo" has everything needed to make a great Verdi opera great: notable roles for lyric tenor, spinto soprano, heroic mezzo, leading baritone and two top-rank basses. The confrontation between these two, in the roles of King Philip II Spain and the Grand Inquisitor, provides one of Verdi's finest moments. There are large choral scenes, including the representation of what some sources report to have been the largest auto-da-fe in history. This wholesale burning of heretics was arranged as a part of the celebration of the marriage of Philip to Elizabeth de Valois, for this opera, like the "Carmelites," has its historical basis.

Written after "Boccanegra," "Masked Ball" and "Forza del Destino," and immediately before "Aida," "Don Carlo" is Verdi at the peak of his epic grandeur. That the Metropolitan is bringing it, together with "Otello," to Wolf Trap this week means that Verdi lovers, like those of Poulenc, will find the coming Wednesday, Thursday and Friday nights irresistible. CAPTION: Picture 1, Jon Vickers is in the title role of Verdi's "Otello."; Picture 2, Opening scene of "Dialogues of the Carmelites": "Nothing composer Francis Poulenc wrote gave him greater pain in its creation, or greater joy when he had finished it, than the 'Carmelites.'"