Opera Orchestra of New York, or OONY, performs two main services: It gives us operas rarely seen in opera houses. (These are concert performances, in Carnegie Hall.) And it gives us singers: sensational ones, often unorthodox ones. OONY is a presenter for voice nuts. And on Tuesday night, they were appeased and gratified.

The opera was, indeed, a rarity, but one that deserves fame: Donizetti’s “Dom Sébastien,” the composer’s last. Donizetti wrote some 70 operas, beginning with “Il pigmalione” in 1816; he penned “Dom Sébastien” — or, more formally, “Dom Sébastien de Portugal” — in 1843. It is a French grand opera, with five acts, ballet, the whole nine yards. (OONY, under its founder-conductor Eve Queler, omitted the ballet.) The librettist for “Dom Sébastien” is the nicely named Eugène Scribe.

And the story? Set in 16th-century Portugal and Morocco, and loosely based on historical events, it’s about Europeans and Moors, at each other’s throats. The Moors scream such lines as “Holy war is declared, and my soul is concerned only with honor.” Too bad these musty old operas are “irrelevant” to the present day.

In the course of the opera, the Inquisition and the Moors compete with each other in cruelty, and, in an apt development, they actually band together. Our heroes are Dom Sébastien, the Portuguese king, and Zayda, a Moorish princess. They love each other, and they die, for this is a “grande tragédie.”

The opera has but one female role, because the original Zayda — a French mezzo named Rosine Stoltz — demanded so. Her boyfriend was head of the opera house. I know you can’t imagine such dealing in the music biz today.

On Tuesday night, Zayda was sung by Vesselina Kasarova, one of the most remarkable singers around. She is well familiar with the role, having sung it at Covent Garden last season. And she sang the bejesus out of it for us.

I have tried to describe this Bulgarian mezzo many times before, and it’s not easy. Her sound is extraordinary, filled with varied colors and qualities. It is beautiful, dusky, lush, ghostly, unearthly, earthy, baritonal, feminine, sensual — you name it. Prior to Tuesday night, I had heard the Kasarova sound only in opera houses (and fairly drafty ones at that). In Carnegie Hall, it was more astounding, and bewildering, than ever.

And Ms. Kasarova knows what to do with her voice. Her technique is secure, and so is her musicianship. She commands her voice like a cellist who has complete control over her instrument. (Han-Na Chang?) In addition to which, her French is clear and good.

Ms. Kasarova was what you might call the top of the ticket, in this election season; but the singers were excellent “down-ticket,” too. Where does Ms. Queler find these voices? Maybe it’s that she tries.

In the part of Dom Sébastien was Dmitry Korchak, a Russian tenor still in his 20s. Mr. Korchak should make a tidy sum in Rossini and Donizetti, which is great, because the opera world can’t live on Juan Diego Flórez alone. Like that Peruvian star, Mr. Korchak has a little quiver in his voice, and it is not unappealing. That voice was occasionally thin and pinched on Tuesday night; intonation sometimes sagged. But Mr. Korchak produced exciting high notes, and generally scored a hit.

In the role of Camoëns, the king’s faithful friend, was the baritone Stephen Powell. What a beautiful voice, and what smooth — ultra-smooth — singing. There were no lumps in the porridge, so to speak. And the high G with which he ended the opera was glorious.

The bad guy in this opera — or one of them — is Juam de Sylva, the Grand Inquisitor. (Hiss loud.) He was sung by the bass Daniel Lewis Williams, who showed just the right combination of menace and elegance: a menacing elegance. His vibrato was generous — not quite overly so — and his lowest notes were very impressive.

Three more beautiful and well-supported voices? Three more capable, even stirring, singers? Stephen Gaertner, a baritone; Philip Cokorinos, a bass-baritone; and Mark Risinger, a bass. There were eight singers on that stage, and not a clinker in the bunch. That, like “Dom Sébastien,” is a rarity.

And I have not yet mentioned one of the singers: Michael Fabiano, a tenor, and still a student. He owns a splendid, arresting instrument, and the skies before him seem very bright indeed.

Ms. Queler conducted as she usually does: with competence, knowledge, and devotion. Occasionally, the orchestra was too loud for the soloists, and even for the chorus. The chorus was strong, by the way: a merger of the New York City Gay Men’s Chorus and the Scott Choral Artists of New York. Orchestra members were uneven, with the oboe having a good night, and the horns an unfortunate one — and so it goes.

Here is a question: Why can’t OONY use supertitles, which we now and then see in Carnegie Hall? That would be so much better than burying one’s head in the libretto (which OONY kindly provides). It could be the union costs are formidable, and nutty.

Look, “Dom Sébastien” is a wonderful opera, and OONY gave us a wonderful night. Sometimes in life, you get your money’s worth, and then some.