JUST AS recently as two years ago the likelihood of a revival of interest in Alfredo Catalani's brooding, verismo tear-jerker of an opera, "La Wally," seemed about as probable as a return to the literary fashion of Sir Walter Scott. And the notion that soprano Wilhelmenia Wiggins Fernandez might become a movie star seemed equally remote.

But now, with the enormous popularity of the movie thriller "Diva," both events have transpired.

In a lush Parisian setting, Fernandez plays the role of a prima donna on the international opera circuit who has a phobia about making recordings. A devout young fan, a French messenger boy, tapes her performance at a recital of the aria, "Ebben? Ne andro lontana," from the first act of "La Wally" and, through various complications, finds himself an innocent entrapped in the bloodletting of an international drug and white slavery ring.

The movie opens with a full performance by Fernandez of the dreamy aria -- the vocal counterpart of something that melts in your mouth -- and parts of it are repeated four more times in the course of two hours of violence and romance.

As a result, the sound-track album is now a best seller. And, after a century of neglect by audiences and opera companies, people are asking why doesn't anybody do "La Wally"?

Since there has never been a commercial recording of the opera, that's not the easiest question to answer. About all that can be found in record stores is a pressing drawn from a primitive tape of a "La Scala" performance on Dec. 7, 1953. The performance is sensational. In the title role is Renata Tebaldi at the peak of her form, with a young Renata Scotto in the pants role of Walter, Giorgio Tozzi as Wally's father, Mario del Monaco as the tenor and no less a figure than Carlo Maria Giulini conducting. But the sound is wretched; sometimes you can barely hear at all, so that for all this array of talent Catalani's opera doesn't get anything like a fair trial. There are, however, separate recordings of the aria on recital discs by, among others, Scotto (CBS) again, and de los Angeles (Seraphim).

For the movie's purposes, why pull an aria out of a mostly forgotten work by a mostly forgotten composer when there are hundreds of arias that are more familiar? The answer, Fernandez has said, is that "Ebben . . . " was chosen precisely because it is less familiar--to preserve the illusion, for many, of movie music.

That the aria, which ends "La Wally's" first act, is quite beautiful is almost beyond dispute. It is a sad, haunting reverie intoned by the opera's melancholy leading lady, in which she reflects that if her father forces her to marry the wrong man she will wander off in the Tyrolean snow and never return:

"I will go alone and as far away as the echo of a church bell . . . "

The melody returns in the orchestra at the third act's end. And all of this is, in the true soap opera tradition of verismo opera, in anticipation of the real end that strikes Wally and her beloved -- as they are swept away in an Alpine avalanche at the conclusion of the last act.

This sad, nostalgic mood also matches the sad, lonely character of Cynthia Hawkins, the diva Fernandez plays in the movie. And, given its eloquence as a display piece for the lyric soprano voice, it is no wonder that Fernandez wanted to sing it. Above the staff there are seven high G's, an A and a climactic high B, which then descends a full octave without a pause for breath. That's the kind of huge interval that will brilliantly demonstrate a singer's evenness of range and breath control, or immediately expose the lack thereof. Fernandez comes off well.

Catalani's close friend, Arturo Toscanini (who named his first daughter Wally), felt strongly that Catalani did not get his due, and was troubled by the composer's tragic death while still in his thirties. It was Toscanini who introduced the opera to this country in 1909, when he was running the musical side at the Met. And, in fact, one of Toscanini's last recordings, in 1953, was of the dark, gloomy prelude to "La Wally's" last act.

This opera was Catalani's last work and is considered his best. There are solid grounds for Toscanini's admiration for it.

The opera deserves to be performed. It lacks the consistent power that seemed to come so easily to Catalani's contemporary Puccini (also a close friend of Toscanini). Nonetheless, "La Wally" is certainly stronger than some of the lesser works of Massenet or Donizetti now enjoying revivals.

But even a Toscanini couldn't make people care about it. It took a French film thriller to do that.