An opera company that brings out the best in its singers

Throughout its 62 years, the San Francisco Opera has had the reputation of serving its art form handsomely. On its own terms, night for night, it has offered most of the important singers of each generation and encouraged and even groomed newcomers. This year I was able to see five of the company's 10 productions in a little over a week. Together, they gave a good sense of present standards in Terence A. McEwen's fifth season as general director of one of the country's three most important opera houses.

The company's major achievement was the revival of Aribert Reimann's shattering 1978 opera, ``Lear,'' with Thomas Stewart in the title role in a Jean-Pierre Ponnelle production. Two noted sopranos assumed new roles for the first time in their careers: Mirella Freni took on Adriana Lecouvreur in Cilea's opera of the same title, and Renata Scotto sang Charlotte opposite veteran tenor Alfredo Kraus in Massenet's ``Werther.'' Eva Marton introduced her celebrated Turandot to the West Coast, aided by Franco B onisolli -- perhaps the only legitimate Calaf of the day. A sumptuous John Copley production of Handel's ``Orlando'' not only boasted Marilyn Horne in the title role, but a young rising star named Ruth Ann Swenson as the shepherdess Dorinda.

With the exception of ``Turandot,'' a tangible ensemble sense presided over each opera. This was most evident in ``Lear,'' as triumphant an evening of new opera as will be seen today. The cast was without flaws. The production used often the simplest of means to evoke a powerful array of visual images. Friedemann Layer's conducting exploited the passionate, brutal, and haunting aspects of the score without once blanketing the singers.

Reimann treated Shakespeare's play as a black study in the various aspects of madness and brutality. The score accompanies and supports the text, rather than commenting on it. Only in the final pages, when Lear mourns the murdered Cordelia, does something like pathos really emerge, to devastating musical effect.

Mr. Ponnelle, the director-designer, captured visually every musical moment. With lighting (by gifted resident lighting designer Thomas J. Munn), sensational costumes (by Pet Halman), and the three-sectioned unit set placed on an otherwise bare stage (back to the fire door), Ponnelle evoked a world of barbarity and pure evil. The 14-member cast was dominated by Mr. Stewart's tour de force. With every aspect of his art challenged, he rose to the demands with arresting splendor. Helga Dernesch and Anja Si lja shone as the evil sisters, as did Sheri Greenawald as the gentle Cordelia. David Knutson made Edgar a bravura display of tenor and countertenor singing and acting.

There is an atmosphere in the house that seems to bring the best out of the stars. Miss Freni blossomed here as I have rarely seen her blossom elsewhere, to create a heartfelt, animated Adriana at once sumptuously sung and imposingly acted. Miss Horne turned in a spectacular performance as Orlando -- rich in nuance and vocal color, and in complete control of the coloratura pyrotechnics and the sustained legato lines. The strength of casting in San Francisco -- with only occasional weak links -- gives ea ch production a particular solidity. The night I heard ``Adriana,'' the often uneven tenor Ermanno Mauro was in magnificent voice; having baritone Leo Nucci as Michonnet for once meant this music would be well sung as well as acted.

In ``Orlando,'' Miss Swenson, a local darling, showed herself a poised singer, secure of her voice and stage demeanor, clearly on the brink of a major career. Jeffrey Gall made a visually impressive Medoro, though he pushed his light countertenor to fill the large theater. Kevin Langan's sonorous bass was stressed only in the uppermost reaches of the role of Zoroastro.

The ``Turandot'' was a more old-fashioned affair. Mr. Bonisolli, a constantly acclaimed singer, has adopted all the behavioral traits of the clich'ed Italian tenor. That his slightly hoarse baritonal voice with its ringing top can often be tapered to something haunting and sensitive was a surprise. Adriana Anelli was the well-intentioned, if bland, Liu. In the tawdry Bliss Hebert production San Francisco uses, Miss Marton could hardly shine to best advantage. But when she launched into the final duet, t he voice soared thrillingly and showed once again why she is acclaimed worldwide in this taxing role.

The ``Werther'' was another memorable ensemble affair on stage. Mr. Kraus has owned the title role for many years, and he was in particularly resplendent form. Miss Scotto, whose detractors always predict vocal catastrophe, proved yet again a mistress of her art. Her first Charlotte pitted moments of insight against moments of tenuousness, some of which was due to Bernard Uzan's uneven direction. But when she is truly comfortable in the role, it will be a youthful and touchingly simple portrayal. Stephe n Dickson was the eloquent Albert, Cheryl Parrish a pretty-voiced, musically substantial Sophie, and veteran Renato Capecchi a wry Bailiff.

The level of conducting is climbing, too. The orchestra has improved annually to the point of real distinction, first and foremost under Mr. Layer in ``Lear.'' Newcomer Maurizio Arena made more of ``Adriana'' than one imagined possible. Sir Charles Mackerras has always known how to make Handel work vividly in a large theater. On the debit side were Berislav Klobucar's routinely conducted ``Turandot'' and the leaden, unpoetic ``Werther'' from Michel Plasson. But even their work did not dim the luster of a company that is functioning on a particularly high level these days.

``Werther'' and ``Turandot'' continue well into the month. The rest of the season (which runs through Dec. 8) includes Verdi's ``Falstaff'' and ``Un Ballo in Maschera,'' Strauss's ``Der Rosenkavalier,'' Britten's ``Billy Budd,'' and Puccini's ``Tosca.''