Opera's big voices - an endangered species?

The reports are in from Bayreuth, the town where Wagner spent most of his last years and where he left behind a theater-shrine in which his works could be performed under ideal circumstances.

Those reports concern the new ''Ring'' cycle staged there this summer. I have no intention of discussing a production I did not see, though most of the reviews have called Sir Peter Hall's production one of the great fiascoes of recent memory (comparable to his Metropolitan Opera staging of Verdi's ''Macbeth'' this past season).

But the Bayreuth ''Ring'' was broadcast in digital FM stereo, and I had a chance to hear it. One aspect of the performance that most of the reviewers had complained about - the lack of Wagnerian voices present - was clearly in evidence.

Where are the big voices today? Will we ever get back to a time when a Kirsten Flagstad could - as anyone who ever heard her will confirm - flood a house with sound? Will there ever be even another Birgit Nilsson, to mention someone from the immediate past? Incidentally, ''Variety'' reported that she has finally sung her last concert, thus bringing to an end the resplendent career of one of the supreme mistresses of the art of singing.

When Leonie Rysanek and Joan Sutherland finally decide to exit - one hopes that will be years away - there is danger that the really large voices ideal for certain slices of repertoire will no longer exist.

Miss Rysanek refers to her breed as a dinosaur. She has spent an entire career as a jungendlich (youthful) dramatic soprano and has never dared assault the heavier roles, such as Elektra (except on recordings), Isolde, or Brunnhilde , roles that managers have been hounding her for years to take on.

Miss Sutherland, who started out being a Wagnerian soprano and then switched to the bel canto coloratura literature with startling success, also possesses a large sound. Last season at the Met in ''Lucia di Lammermoor,'' she sat on stage near the end of the first act, singing at half volume, and one was aware of her voice effortlessly expanding into the theater. And when she chose to let go at full tilt, the sound shot through the hall.

Why is it that this type of voice is virtually nonexistent today? At Bayreuth - and every place Wagner is performed - we have to make do. Hildegarde Behrens, Bayreuth's Brunnhilde, surely turned in a blazing performance - interesting, committed, dramatically alert and alive. It was made all the more remarkable in that she had never sung any of the Brunnhilde roles before.

But Bayreuth's acoustics are exceptionally generous for the singer. Even small voices sound rich on that stage, and when a young, unformed lyric tenor makes the leap from Bayreuth to a larger house, the voice is suddenly shown for what it is, especially if it's thin and hollow.

We haven't had a genuine heldentenor (heroic tenor) since Melchior. The world at one time used to ''make do'' with Wolfgang Windgassen, and that was not a half-bad thing. Now the singers are Rene Kollo, Siegfried Jerusalem, and Peter Hoffmann, who would be singing operetta rather than opera in a saner, more suitably populated vocal world.

Miss Behrens would, in that saner world, be focusing on Mozart and Strauss, and perhaps an Elsa (''Lohengrin'') or something similar. And now she is singing Brunnhilde, Isolde (in concert, preparing for a recording led by Leonard Bernstein and, next season, a Met performance), and any number of other things. The voice is showing signs of the pressure.

The other hope for the big roles is Eva Marton, who sings her first Brunnhilde in ''Siegfried'' in San Francisco this coming spring. It may be a bit too early, but the voice certainly has the strength, the steely thrill, and the power to ride a large orchestra effortlessly.

Both these ladies have been singing for a while now, though they both appeared to have come out of nowhere in Europe. Nowadays, young singers are expected to be fully matured, finished professionals by the time they reach 30. Yet big voices rarely come into complete focus for another 10 years, and by then those young singers who might have progressed are at the ends of their careers - victims of the too-much-too-soon syndrome that seems to have polluted so many of our lively arts today.

Something has to be done if Wagner is to have a place even in smaller opera houses. Short of giving singers hand mikes, there is no other solution but to try to spot voices and then cultivate them - in secret, if need be - until they are ready. It is now up to the general directors of the opera houses, and to conductors as well, to ensure the future of voices. It would be best to return to the custom of the old days when the maestros nurtured, coached, protected, guided.

Surely that route is not the one chosen by Solti. In his handsome concert presentation of ''Das Rheingold'' with the Chicago Symphony this past spring in Carnegie Hall, he made some peculiar choices for roles, such as the light, thin mezzo Jan de Gaetani as Erda, which should be a full contralto role. (On the other hand, Siegmund Nimsgern sang the Wotan role marvelously well until the closing pages. And Hermann Becht's dazzling Alberich and Siegfried Jerusalem's mellifluous if under-characterized Loge added lustre to the evening.)

Solti's way with Wagner - and particularly with his superb orchestra - may be brass-heavy, but it is thrilling. Yet when a conductor is asking for so much orchestral ''noise'' - and Wagner needs that noise - he needs the voices to go along with it.

So the order is tall, but it is also imperative that it be worked on with all due speed.