ot every important revival or new production is accompanied by a recording-a great chance was missed with Boris Godunov-but the Met and its listeners have been lucky with I Vespri Siciliani, Death in Venice and most recently The Siege of Corinth. As with 1 Vespri Siciliani, it comes as something of a shock to discover a major neglected score, a fitting companion piece to Guillaume Tell, which was made newly available on records last season. Predilections of the standard audience, plus exigencies of the marketplace and the mentality of the more routine sort of performers, have lulled us into almost believing the bromide that “If something isn’t performed, there is a good reason.”

In the case of L’Assedio, the main reason has been the unavailability of qualified singers. Angel’s cast, identical to the Met’s in its longest roles, meets most of the score’s requirements, even in a version that tends to complicate rather than simplify Rossini’s ornate line. Some singers (the men) are less to the coloratura manner born than others, but all sing their murderous roulades without flinching. The flashiest moments are not always the most effective: Justino Diaz makes a memorable impression in the beautiful cantilena of the accompanied recitative in his first scene, limning a conqueror on a broad scale, and the moments of prayer create a needed oasis of depth amid the pomp and panoply of so grand an opera. In music like this, as in I Puritani (reviewed herewith), it is not enough to’ have a star or two and a supporting cast.

The role of Cleomene is important, and Harry Theyard invests it with an authority befitting the character. For the four shorter roles, Angel has chosen singers locally available in London, where the recording was made, and one of them-Gwynne Howell as Jero-makes a great deal of his dignified aria toward the end of the drama, singing with crisp, incisive and compact tone.

Granted that such a cast of males does much more than “support,” the lion’s share of fireworks still falls to Pamira, especially in this generously embellished and augmented edition, with its high D’s and E-flats showering like a sunburst. Beverly Sills handles her role with valor and unflagging intelligence. There are a few tired or uncertain sounds, but the motivation and technical eclat of the whole do show an artist in full command.

The trouser role of Neocle is printed in two versions running concurrently, one for contralto and one for tenor; Shirley Verrett, who is neither, alternates between these, choosing what best suits her firm, rich hued voice. Especially well done is the cabaletta, “E d’un trona alla speranza,” of her scene that opens Act III. The energy, resiliency and subtlety needed to keep this large-scaled epic in motion are provided by Thomas Schippers, who plays the overture in such a way as to arouse anticipation rather than as an end in itself.

In other words, the work is not treated piecemeal but with the grand overview needed to make it come alive. And the music itself, possessed of many a harmonic and instrumental subtlety, lives up to its advance billing as a major rediscovery. The recording engineers have coped well with the large forces, but the “collapsing” sound effects at the end, aside from being dramatically ineffective, cover the music too much.