COMMENTARY : ‘Lisbon Traviata’: The Operatic Perspective : Stage: Playwright Terrence McNally knows his opera. He is erudite and passionate and, like the characters at the core of his play, obsessed with Maria Callas.

Terrence McNally--whose “Lisbon Traviata” is beguiling, bemusing, amusing and shocking audiences these days at the Mark Taper Forum--knows his opera.

He is erudite and passionate. It is a nice combination of virtues.

A frequent guest on the quiz programs that take up the second intermissions of Metropolitan Opera broadcasts, he can be counted upon to reduce his fellow “experts”--especially this one--to tongue-tied dunces. Quick, serene and boundlessly articulate, he instantly recognizes even the most obscure snatch of melody, invariably recalls the most arcane minutiae regarding dates, titles and plot structures.

What’s more, he demonstrates his intellectual prowess with a persuasive semblance of modesty and an abundance of easy charm. It is maddening.

McNally is not above making fun of opera and its practitioners. Remember “The Ritz,” with its inspired Zinka Milanov Look-Alike Contest in the men’s sauna? Essentially, however, he does not regard any pursuit of the lyrical muse as trivial.

Like the sympathetic, tormented, obsessive characters at the core of “The Lisbon Traviata”--a play that begins as an unreasonable facsimile of opera buffa and ends in the throes of verismo tragedy--he measures time, and life, in serious terms: BC and AC.

Before Callas and After Callas.

“Maria Callas,” he reflects in a program note, “was the greatest singer of all time.”

All time. Period.

“She sang,” he writes, “as if song were the most natural way imaginable of expressing our inner lives.” For McNally, “opera is theater,” and, although he doesn’t come right out and say so, theater is life. “I can’t stand it,” muses his quasi-hero, “without music.”

One doesn’t have to be Callas-crazed to appreciate the verities of “The Lisbon Traviata.” Nor does one have to be gay or chronically fanatic in matters operatic, as the protagonists happen to be.

Still, a little knowledge of what Henry Fothergill Chorley called the most irrational of art forms is useful. It helps the observer spot psychological clues and narrative subtexts.

The first act is, essentially, an extended duetto per due gatti . It abounds in canny, catty asides, most of them concerning would-be Callases. Montserrat Caballe, we are told, is a dull diva oddly prone to cancellation. Eva Marton has made a career of screaming. Beverly Sills’ sweetheart image was eventually compromised by a wobble.

Not everything rings true here. It seems unlikely that any well-informed, self-respecting opera queen would speak of Victoria dee los Angeles, Cherubini’s Med eeya or Renata Teb awl di, much less “La Travia da .” And no decent Callas-worshiper would get the intervals wrong when mimicking her performance of “In quelle trine morbide.”

Oh, well.

McNally’s buddies in babble are most convincing when they are nasty. Marilyn Horne, they agree, “sings like a truck driver.” Still, they manage a realistic appraisal of her abiding vocal weakness: a tendency to sing flat. Not many groupies, or critics, have been that perceptive.

The boys in McNally’s band act out mortal operatic confrontations with sophisticated aplomb. Nathan Lane as the magnificently hysterical Mendy plays a vindictive Tosca to the gurgling Scarpia of Richard Thomas--cast as the seemingly controlled Stephen.

Later, incidentally, Thomas drops a hint of the ballet in his family background. When Stephen finds someone else’s undergarment left indiscreetly in his living room, he kicks it under the table with exquisitely graceful disdain worthy of Robert Helpmann.

Thomas and Lane move from Puccini to Bizet. Fatefully, they impersonate “that fun couple,” Carmen and Don Jose.

We hear Carmen’s final words of defiance to her lover, before he becomes her murderer: “Frappe-moi donc ou laisse-moi passer!”

Only the operaphiles at the Taper recognize that line when, none too subtly, it recurs in English at the end of “Lisbon Traviata.”

“Kill me now, or let me pass,” cries Stephen’s former lover, Mike (Dan Butler). He flings his ring at Stephen and tries to leave their apartment for a rendezvous with another man.

In this instance, the imminent violence is signaled immediately. In the recent New York production, for which McNally favored a less bloody denouement, the “Carmen” references served as a jarring false-alarm.

The bleak half of “Lisbon Traviata” contains numerous operatic references, most of them subtler than the terminal invocation of Bizet. When the desperate Stephen first contemplates mayhem, he puts “Wozzeck” on the turntable. When he wants to avoid the pain of crucial questions, he plays the “Lohengrin” prelude.

At the final blackout, he cradles his beloved, pathetically mouthing the giddy words sung by Callas in a significant recording of “La Traviata.”

“Che far degg’io? Gioire! Di volutta ne’ vortici perir! Gioir. . . .”

“What should I do?” Verdi’s tragic heroine asks herself. “Find joy. Plunge into the vortex of pleasure and die there. Joy. . . . “

And what, the non-aficionado may ask, is the significance of Lisbon in “The Lisbon Traviata”?

McNally’s title refers to a pirated recording that documented a live Callas performance at the San Carlos Opera House in Portugal, anno 1958. At the time when the play was written, the Lisbon “Traviata” was excruciatingly difficult to find, even in emporia that specialized in under-the-counter rarities. Mendy wasn’t the only Callas collector who created mad scenes trying to get his hands on the illicit set.

Now, it happens to be available commercially at any friendly neighborhood record store. EMI/Angel managed to acquire the rights a few years ago, and has issued the Lisbon “Traviata” both on CD (7491878) and LP (DSC 49187).

The operatic fates, alas, are cruel. It isn’t a very good performance.