Ten Minutes, Mr. Domingo : Ever wonder how a supertenor prepares for opening night? Let’s spend some time with Placido Domingo as he rehearses Verdi’s ‘Stiffelio’ for L.A. Opera.

In a rehearsal room at the Dorothy Chandler Pavilion, a new Three Tenors concert is being readied for a waiting world. No, not those three tenors, but three slightly less celebrated vocalists named Dan O’Callahan, Michael Canales and Nova Safo, who are preparing to appear with the Barrio Symphony in a free performance at Echo Park.

Into the room strides Placido Domingo, invited earlier that day to visit the rehearsal--and doing a double take when he gets a look at the Three Tenors title on the group’s flyer.

At the urging of conductor Peter Quesada, he agrees to hear the 17-year-old Safo sing “Una furtiva lagrima,” the exquisite lyric-tenor aria from Donizetti’s “L’Elisir d’Amore.” But with the orchestra’s bassoon player temporarily out of the room, how is the aria to receive its proper introduction?

With Domingo crooning the bassoon part, that’s how. In an innovation he has yet to share with Messrs. Pavarotti and Carreras, Domingo serves as instrumental stand-in on behalf of his teen-age counterpart.

When the singing stops, he offers congratulations all around, signs autographs, poses for photographs and sweeps away, leaving plenty of stardust behind.

A few hours earlier, his own rehearsal for the Los Angeles Music Center Opera production of “Stiffelio” had also found him signing autographs and posing for snapshots with members of the orchestra in breaks between acts.

“Whenever he comes back, there’s a great lift of spirits,” says L.A. Opera General Director Peter Hemmings. “He has become a friend to all the longtime members of the company, and when he comes to the first rehearsal, everybody feels cheered up.”

And probably greatly relieved in this case. After all, Domingo has arrived just one week before opening night--nearly a month after the chorus started work on “Stiffelio” and three weeks after the orchestra first began to explore this unfamiliar Verdi score. The initial staging rehearsals with the chorus and other principals soon followed, and the stage crew then loaded in the sets (from the Royal Opera House, Covent Garden) and held basic tech rehearsals.

At the Sitzprobe (literally, “sitting rehearsal”), the first full-cast run-through with orchestra, Domingo enters the Grand Hall of the Pavilion during a dramatic moment in the overture, first waving to friends, then kissing and hugging the sopranos seated on both sides of him and delivering an especially emphatic handshake to baritone Vladimir Chernov.

In loose white shirt and pants over brown loafers (no socks), he looks relaxed and tanned, sometimes briefly putting on the glasses that hang around his neck and peering at the score on the music stand in front of him.

Domingo, 54, is a veteran of three different “Stiffelio” stagings during the past two years--including recent London performances of the version being presented in Los Angeles. But the Sitzprobe gives him another opportunity to address musical issues without the demands and distractions of the staging, and he makes the most of it.

During orchestral passages, he taps his toes or plays along on an imaginary guitar. But he remains thoughtful and absorbed during other singers’ music and increasingly intense during his own, rocking convulsively in his chair, as if caged, during Stiffelio’s agonized confrontation with his wife in the last act.

Watching Domingo onstage and backstage at the Pavilion over a four-day period, from the “Stiffelio” Sitzprobe to the dress, puts the man’s character in high relief: a charming, energetic social animal, utterly comfortable with his celebrity; an affectionate family man; a sober and sometimes withdrawn artist, focused on the highest standards of opera.

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Composed in 1850, between “Luisa Miller” and “Rigoletto,” “Stiffelio” was virtually a lost opera for more than a century. It concerns an Austrian clergyman with an unfaithful wife--a subject scandalous enough in 19th-Century Italy to inspire crippling censorship problems that prevented it from being performed in its original form.

Seven years after its premiere, Verdi gutted the “Stiffelio” manuscript and reworked the opera as “Aroldo,” defrocking the title character and making him a British knight back from the Crusades. Only in the late 1960s did full scores of “Stiffelio” again come to light.

Verdi scholars generally concede that the earlier work is superior, though Domingo is quick to mention that “Aroldo” has a big tenor aria and “Stiffelio” doesn’t. “I’m hoping one day we can put that [“Aroldo”] aria into ‘Stiffelio,’ ” he says after the Sitzprobe . He nods in agreement at a mention of the title character’s similarities to Otello (perhaps his most celebrated interpretation) but speaks of the opera more in terms of its vocal challenges than character issues.

“One thing I want to mention,” he says, “is that when you talk about bel canto, I think people forget that Verdi [in this period] is bel canto too--king-size bel canto.”

“The [title] role needs a dark sound, but the tessitura is quite high,” he continues. “I think there are maybe six or eight A-naturals [for the tenor] in all of ‘Tosca’ but as many as 60 in ‘Stiffelio.’ ”

Domingo’s emphasis on vocal altitude may be significant because he began his singing career as a baritone and, as Peter Hemmings explains, “people often say he has a baritonal quality to his voice, that he is happier in the slightly lower parts.

“I interpret that differently. I feel he is happier in parts that require real involvement and histrionic ability--Otello, of course, and to lesser extent, perhaps, Jose in ‘Carmen.’ Those are roles with which he is really able to identify.”

Altitude, however, can sometimes be daunting. In his forthcoming book “Sopranos, Mezzos, Tenors, Bassos and Other Friends,” former Metropolitan Opera General Manager Schuyler Chapin writes that during the 1973-74 season, Domingo pleaded to be released from a performance of Verdi’s “Il Trovatore” because the aria “Di quella pira”--with its celebrated high C--terrified him:

“He sank to his knees and, clasping his hands together, began to pray at me,” Chapin writes. “ ‘Please,’ he begged. ‘Let me cancel tonight. I can’t face that aria again.’ ”

Chapin reports that Domingo eventually agreed to perform only when another tenor was stationed in the orchestra pit prepared to sing “Di quella pira” in Domingo’s place if he wasn’t up to it. In that case, Domingo would merely mime the aria.

Domingo remembers the situation very differently. He had a cold and was indeed worried about that “Trovatore,” he recalls, “but on my knees is a little exaggerated.” And the substitute tenor in the pit? “Ridiculous,” he answers. “I wouldn’t go onstage and ask someone else to sing. That’s totally imaginary.”

But what about the larger issue: Has he ever been too scared to sing, afraid of cracking on a high note, of going onstage in one of the really killer roles of his repertory: Otello, Siegmund (in “Die Walkure”), Samson?

“I think it’s only frightening when you’re sick,” Domingo declares. “Otherwise I can hardly wait to get onstage.”

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The words placido domingo mean “peaceful Sunday” in Spanish, but there’s nothing peaceful about the two-part 2:30-to-10 p.m. Sunday stage rehearsal that will see the complete cast, in full makeup and costume, working through “Stiffelio’s” every detail.

Specifics of all sorts must be nailed down--from exactly where the chorus members (the clergyman’s congregation) should pick up their prayer books to exactly what soprano Elena Prokina should be feeling and doing as the minister’s repentant wife in the final moments of the opera.

“These double rehearsal days: That’s one thing we have to get rid of [at L.A. Opera],” Domingo comments to more than one colleague in his capacity as both performer and the company’s official artistic adviser. “By the time you get to the evening, you cannot sing any more.”

The second act will be rehearsed twice, and Domingo asks conductor Edward Downes to allow his “cover,” or understudy, Timothy Mussard, to sing the repeat. Not so much to spare himself, he explains, as to give Mussard a chance to rehearse with full orchestra. Downes consents, and Mussard responds with a performance of full-out intensity.

Installed in the dressing room with the name of the Philharmonic’s Esa-Pekka Salonen on the door, Domingo shares the day with nine members of his family--among them his wife, Marta, two of his three sons and all three grandchildren. “I lost my mother a year ago,” he says, “and it makes you want to be closer to those you have when you lose someone. So that’s the reason we try to be together.”

During his free time in L.A., Domingo and his family have watched the U.S. Open on television in their apartment downtown and gone to the movies at the Universal Cineplex--where half the group (including him) ended up at “Babe” and the others (including Marta) at “Desperado.” (The Domingo family headquarters is in Acapulco; there is also an apartment on Manhattan’s East Side.)

During this long day, as he shuttles between the stage and dressing room, a parallel develops between Domingo and the character he portrays. Both are charismatic public figures who energize a large number of colleagues and followers. Both also work hard at balancing the demands of their profession with their family relationships.

“I try to live a very normal and natural life,” Domingo says. “If you are known [to the public], you cannot say, ‘I wish I was not known now.’ You have to live with that. And if you want to be private, you can be. Some people are never left in peace, because they really don’t want to be.”

When Domingo wants his privacy or is feeling protective of his family, his dressing room door closes. But much of the day, it remains open and he receives visitors cordially--among them L.A. Opera artistic administrator Robin Thompson, who has brought along a 19-year-old Latino man who works at the downtown YMCA and just might need his cultural horizons broadened.

A private tour of the Pavilion and a meeting with a Latino superstar is what Thompson has in mind, and Domingo cooperates fully by talking with the young man in his dressing room.

“Placido loves anything that concerns young people and Mexico,” Thompson says later on, “and it’s very typical of him that he makes time for things like that. There are not very many singers who would.”

O bviously, Domingo’s sense of connection to other Latinos can be traced to his background in Spain (where he was born in 1941) and Mexico (where he lived from age 7). His parents specialized in the zarzuela--an immensely popular form of Spanish-language operetta.

Growing up in that world--and working as a nightclub singer-pianist in his teens--certainly gave him a broader perspective on singing than a conservatory-cloistered student might have. But his talent for serious music became evident very early on and he studied both singing and conducting in Mexico City.

Now he can look back on such career extremes as singing Wagner at Bayreuth and pop hits with John Denver; making operatic films with Franco Zeffirelli and television extravaganzas with Pavarotti and Carreras; plus a 10-year relationship behind the scenes and in the spotlight at L.A. Opera.

Does he spread himself too thin? Perhaps, but he says the variety in his career invigorates him, and he believes that his pop or crossover projects have brought huge new audiences to opera.

“Some people,” Domingo says, “do not like it, but many more people do.”

A bout 100 young people have been invited to the “Stiffelio” dress rehearsal, some of them as part of community outreach programs begun by Domingo. Others have come at the behest of his 36-year-old eldest son, Jose (a.k.a. Joe, a.k.a. Pepe), who works locally in the audio industry.

Tots from the Hogg’s Hollow Preschool in La Canada Flintridge and older children in the performing group Kids on Stage for a Better World, based in La Crescenta, mingle in the foyer at intermission when Domingo comes in to greet them.

“Next year, they have to come to ‘Pagliacci,’ ” he tells Jose, embracing whole armfuls of kids all at once and, in his ecclesiastical stage attire, creating a major “Suffer-Little-Children-to-Come-Unto-Me” photo-op.

The dress rehearsal proceeds without crises, and at the end Domingo stays in character long enough to make the sign of the cross over the orchestra. It’s an affectionate joke that pays tribute to the players’ hard work on “Stiffelio”--work that comes at a time when many of them, along with members of the chorus and stage crews, also are involved in a brand new production of “Der Fliegende Hollander.”

I n his Sept. 9 “Stiffelio” review, Times music critic Martin Bern heimer would say that “Domingo brought extraordinary intensity to the plaints of the tortured hero, and extraordinary poignancy to his insecurities. The tenor sang, moreover, with the plangency of a fine Otello coupled with the legato finesse of a fine Duke of Mantua. The recent reports of his vocal distress are wholly unwarranted.”

Some of those reports arose when Domingo canceled nine European performances this June on doctor’s orders. As he explains it, he had caught a cold from airline air conditioning early in the year and never had time to get rid of it.

“The whole time I was in Los Angeles [for “Otello,” in early May] I was sick,” he says. “And when I was in Madrid singing ‘Stiffelio,’ after the third performance, I said, ‘That’s it.’

“I didn’t cancel here, because it is a company that is so important for me--I hate to disappoint the public. But eventually I had to cancel.”

Domingo served as a member of the L.A. Opera board before the company existed as a producing-performing entity, and he says that he and Hemmings have achieved “the perfect blend of Anglo-Saxon and Latin temperament that we need. You have the feeling of being in a family here.”

Besides artistic adviser, Domingo holds the title of principal guest conductor, and Hemmings says he is consulted on all artistic matters, “not just the ones involving his own performances. He is always full of productive and useful ideas.

“I can’t imagine our company without his involvement,” Hemmings continues. “I reckon he gave us a 25% head start in what we did here--initially because of his actual involvement with the company, the fact that he sings with us. But his presence also makes it more attractive for other famous singers to sing here. He’s a very real presence in our company.”

Hemmings says Domingo has dates worked out with L.A. Opera through the 1998-99 season, but Domingo speculates that he may have to re-evaluate his commitments in light of his new responsibilities as artistic director of the Washington Opera. “The 1996-97 season is my first [as artistic director],” Domingo explains. “I don’t know what the situation will be once I start. I’ll have to see how I cope there.”

Hemmings notes that Domingo’s main involvement with Washington Opera will be in November, which neatly dovetails with his continuing performance schedule at the Metropolitan Opera in New York.

And his future as star tenor? “As things are going now,” Hemmings says, “I see him singing at least another five to 10 years.”

But Domingo is taking it step by step.

“I’m happy to arrive at the maturity of my career and still be able to sing and do beautiful things,” he says.

Yes, he still hopes to include Wagner’s mighty “Tristan und Isolde” in his repertory before he’s through--though he has canceled plans to make the attempt in Vienna next year.

“Now I’m just singing the second act in concert form and then recording the whole opera,” he says. And there’s more rare Verdi in his future: “I Masnadieri,” perhaps at Covent Garden. Plus a Three Tenors tour that he says he’s not yet at liberty to discuss.

What would he change in his professional life at this point?

“I would like to leave time for improvisation,” he answers. “Everything is scheduled so far in advance. I understand why, because as the artistic director of the Washington Opera I am now booking artists for 1998, ‘99, 2000. I have to, but I wish there were another way. . . .”

A fter the “Stiffelio” dress re hearsal, well-wishers throng backstage to meet Domingo, who welcomes them with warmth and patience outside his dressing room. Suddenly, a little girl in the crowd stops all the congratulatory chatter dead in its tracks with a pertinent question:

“Are you Superman?” she asks Domingo loudly, staring deeply into his eyes. He laughs, not understanding what she means, and she touches his cape-like minister’s robe to explain herself.

“No, I’m not Superman,” he says to her tenderly. “And no, I won’t try to fly.”

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L.A. Music Center Opera, Dorothy Chandler Pavilion, Music Center, 135 N. Grand Ave. “Stiffelio,” with Placido Domingo, Elena Prokina, Vladimir Chernov, Tihana Herceg, Jonathan Mack, Kenneth Cox; Edward Downes, conductor; David Edwards, stage director. Tuesday and Friday, 7:30 p.m. $15-$120. (213) 365-3500.