The Orchestra of St. Luke’s becomes the St. Luke’s Chamber Ensemble, when it wants to. Or is it the other way around? Anyway, St. Luke’s is celebrating its 30th anniversary, and it has been appearing at Carnegie Hall. Last week, the orchestra, conducted by Sir Roger Norrington, performed in the main auditorium; countertenor David Daniels was their guest. Two nights ago, the chamber ensemble – which represents the “artistic core” of the orchestra, as St. Luke’s literature says – performed downstairs, in Zankel Hall; Mr. Daniels was again the guest. It was an interesting concert, whose program consisted of two composers only: Bach and Alessandro Scarlatti (Alessandro being the father of Domenico, author of all those splendid keyboard sonatas).

The evening began with Bach’s Concerto for Oboe d’Amore in A major, BWV 1055.We know this primarily as a keyboard concerto, so it was nice to hear it in another (and older) guise. It is an Italian – Vivaldi-style – concerto, but it is Bach through and through. (Typical of Bach that he out-Italianed the Italians, when he was in the mood.)

The soloist was Stephen Taylor, oboist of St. Luke’s, and many another ensemble. Strange about the oboe d’amore: Despite its name, there is often not much love in it. The instrument is often played coldly, wanly, off puttingly. But Mr. Taylor handled it with warmth and verve. Moreover, he is a talented musician, alert to a score’s requirements. The middle movement of this concerto is a beauty in F-sharp minor, and Mr. Taylor sang it nicely – reminding us that it is an aria, in a way. The last movement, he played gaily, skippingly.

As for the St. Luke’s Chamber Ensemble, it played very much in the “period” style, whether or not we would call this outfit a period group. Often, it was rough-sounding, and it could have been more precise – but these are knowledgeable, commendable musicians.

Mr. Daniels was on hand for a motet and a cantata of Scarlatti, and he sang them surpassingly well. The motet was “Infirmata, vulnerata,” its text in Latin. It was interesting to note, right off, that Mr. Daniels’s sound was not dissimilar to that of the oboe d’amore, which had just left the stage. And yet, what is truly similar to Mr. Daniels’s voice? It is one of the most unusual, and greatest, in the world today. Besides which, Mr. Daniels is a very smart singer. This music – like most of the music he sings – was clear, balanced, and exquisitely phrased. The words may be on the trite side (“Strike, wound, pierce my heart”), but Mr. Daniels rendered them nobly, affectingly.

He has the gift of “hugging the line” – the musical line – which is not common for a high voice. Then again, Mr. Daniels boasts a substantial lower register too, as he showed in the motet. As for his technique, it is about as nimble and flexible as they come. Someday, we may have to ask the question: What is it about the American South that throws up one singer after another? (Mr. Daniels is from Spartanburg, S.C.)

Following that first Scarlatti work was another Bach concerto, this one the well-loved Concerto in A minor for violin. The soloist was Krista Bennion Feeney, for over 20 years a co-concertmaster of the Orchestra of St. Luke’s. She gave a fine account of this concerto, displaying an able technique, de spite a few glitches. In the slow movement, she took full advantage of Bach’s modulations. It was sort of funny: Ms. Feeney’s sound said Original Instruments, but her interpretation said Free and Easy. In other words, she played this movement quite liberally – in tempos, in phrasing – but evinced a throwback sound.

When Mr. Daniels returned, it was for the Scarlatti cantata “Perche tacete, regolati concenti?” This, as you can see, has an Italian text, and Mr. Daniels is outstanding in this language: crisp, and lovely, and striking. His diction is correct, but not overbearing – he doesn’t sock the consonants (unless it helps, musically). Also, Mr. Daniels has at his disposal a variety of vocal colors, several of which he employed here. In everything, he was pure – and in some things he was heartrending. The Largo aria “Dormi, ma sappi almen” was close to devastating.

I thought he would have to repeat the final aria – quick and defiant – for the crowd was roaring, but he left the stage … so that the ensemble could get on with one of the Brandenburg Concertos.

This was No.5,in D major, whose first movement is one of the happiest stretches of music extant. Would these players recognize that, and reflect it? Or would they sort of grunt and grind their way through? The former, thank goodness. The flutist, Elizabeth Mann, and the violinist, Mitsuru Tsuboda, played well individually, and coordinated nicely. The harpsichordist, Robert Wolinsky, played sensitively but not bashfully, and he showed ample virtuosity. In the second movement, particularly, Ms. Mann gave us a wonderful sound – almost a virile one. And in the closing allegro, all danced in a becoming, sprightly fashion.

Just as they were reaching the finish line, Ms. Tsuboda had a string snap. Better then, than earlier! It was almost a celebratory moment for St. Luke’s – think of a champagne bottle – in this, its 30th-anniversary season. An honored New York institution, St. Luke’s should have many more. Seasons, that is – in addition to broken strings.