After Monday's splendid "Rosenkavalier," last night's Metropolitan Opera production of "Adriana Lecouvreur" was inevitably a letdown.

The opera itself is not in a class with the Strauss-Hofmannsthal masterpiece and the performance, while acceptable enough, stayed firmly below the highest levels of excitement.

Still, the audience (a bit below capacity) seemed to enjoy itself thoroughly. Applause was generous, particularly for Renata Scotto in the title role, who earned a warm ovation and several bouquets from the audience.

"Adriana" is the only, rather tenuous, claim to immortality of composer Francesco Cile a. It has some fervent admirers, but its place in the standard repertoire is marginal. A number of star sopranos have kept it alive because they have seen a good vehicle for themselves in this opera about an actress.

It is sometimes described as an opera with one Big Tune, but actually it has several. The music is usually well-paced, pleasant and dramatically effective when it is not rising to great lyric heights, as it does notably in Adriana's "Io son l'umile ancella" (Act I) and "Poveri fiori" (Act IV). The heroine also has a fine, lingering death scene and a marvelous bit of spoken declamation at the end of Act III.

The opera offers some fine moments in supporting roles, notably those of the villainous Princess de Bouillon (sung powerfully but not subtly last night by Bianca Berini) and Michonnet, the aging stage director who is quietly, hopelessly in love with Adriana. This role was sung reliably but a bit stiffly by Sesto Bruscantini, who explored only a fraction of its possibilities. And, of course, there are the hors d'oeuvres--notably an Act III ballet about the Judgment of Paris, which worked quite well last night, and a cute little four-part satirical song in Act IV that gives a moment in the spotlight to some deserving people in small roles.

Finally, there is the backstage atmosphere of Act I, which is set in the green room of the Come'die Franc,aise during a performance in 1730. This is very well handled in the Met production, with colorfully costumed dancers exercising and prancing about, a flirtation going on in one corner, a chess game in another, bouquets being carried through the room, actors and actresses making exits and entrances. It has so much life and excitement (without losing focus) that it makes the remaining acts seem a bit drab when "Adriana" settles down to the business of being a serious opera.

Scotto is a good compromise for the role of Adriana, offering a lot of dramatic intensity a la Callas and a lot of fine singing a la Tebaldi. Last night was not one of her great performances, but a good average one. A few moments of barely perceptible insecurity near the beginning disappeared soon and she was particularly fine in the last act.

Next to Scotto, the most satisfactory casting was that of Ara Berberian and Anthony Laciura in the secondary roles of the Prince and the Abbe'. Both were as effective dramatically as they were vocally.

Tenor Neil Shicoff, as Maurizio, spent a lot of time singing on his knees, which earned considerable applause at first. By the last act, he finally mastered the art of singing below mezzo-forte.

Conductor Michelangelo Veltri paced the performance well but did not always keep the orchestra from submerging the voices.