BERLIOZ: Les Troyens. Jessye Norman, Tatiana Troyanos, Placido Domingo, Alan Monk, Paul Plishka, et al.; Metropolitan Opera Orchestra and Chorus, James Levine conducting. Bel Canto Video 12509 (two cassettes, subtitled) $39.95.

Of all the masterpieces of Hector Berlioz, none - no, not even the "Grande Messe des Morts" - is more imposing than his opera "Les Troyens," or "The Trojans."But you may not know it that way. Even during the composer's lifetime the work never had a full hearing, having been chopped into two separate pieces, "La Prise de Troie" and "Les Troyens a Carthage." And of these only the latter enjoyed any exposure until the 1890s, and that largely in a corrupt and otherwise mutilated edition.

Not until 1957 - nearly nine decades after Berlioz's death - was the work presented in anything like the form he had envisioned, under Rafael Kubelik at Covent Garden. Revived in 1969 under Colin Davis for the Berlioz centenary, that production provided the basis for the first complete recording, still one of the monuments of the Philips catalog (and newly available in an outstanding CD transfer). And for once "complete" meant just that, sparking an interest in the rest of Berlioz's operas that, happily, has yet to subside.

What concerns us here, however, is not the Davis recording but a record of yet another complete performance, from Paramount Home Video on its Bel Canto label, one of several new "Live From the Met" issues drawn from the best of that much-acclaimed series.

I was especially happy to see "Troyens" on the list, as locally KUED's one-time-only relay of this performance, in 1983, was interrupted by a power failure. (interestingly, a similiar problem seems to have afflicted things on the Met's end as well, as the tape box notes a section of Act 2 - Berlioz's Act 3 - had to be spliced in from an earlier performance.)

Even then it was clear this was a spectacular production. What is even clearer on re-exposure, however, are the opera's musical strengths, thanks in part to the caring leadership of conductor James Levine. His conception may be less atmospheric than Beecham's (cf. "The Royal Hunt and Storm," where the latter is positively magical) or, in its more classically direct way, Davis'. But he is invariably alive to the music's dramatic import, as well as its structural unity - an impressive feat, given its four-hour running time.

Nonetheless, it is Jessye Norman's Cassandra who dominates things physically and vocally in Part 1, an epic depiction of the fall of Troy. The voice itself is magnificently sumptuous and secure. Yet within that compass she is able to suggest both the tragic foreboding and eventual yielding to fate that is her lot and that of her people. Nor is her stage presence a liability, her stately bearing lending her substantial frame a dignity and majesty that contrast effectively with the chaos taking place around her.

Similarly Placido Domingo, as Aeneas, seizes one's attention from the first. His tenor may be less smoothly insinuating than Jon Vickers', on the Davis recording, but its ringing heroism registers as strongly amid the flames of Troy as in the pastoral beauties of Carthage.

Given her name, I suspect Tatiana Troyanos may have felt a special identification with this work. Whatever the reason, this performance finds her singing with greater ease and freshness than has sometimes been the case, a strong if not ideally ravishing Dido, whose only real failing is a certain want of vulnerability. Surely her abandonment by Aeneas should touch the heart more profoundly than Cassandra's sacrifice, as she too accepts her destiny.

By the same token, the Met apparently knew it had something special here (this was, in fact, the production selected to open its Centennial Season) - witness the number of camera angles designed to show off the depth of the staging as well as its luxuriance. At the same time personalities are kept in the foreground as the larger events that engulf them play out their course to the sides and the rear.

That seems to me a fair approximation of Berlioz's aims, as the opera's quieter, more introspective pages stand out from its larger, more overtly heroic gestures (a case in point: Hylas' melancholy song in Act 5). If Part 1 recalls in places the first two acts of "Aida" and Part 2 the more amorous sections of "Samson et Dalila" - well, we would do well to remember that, although it has taken us a century or more to realize it, as with so many things Berlioz got there first.