He had played concertos in New York, but never a recital — and Sergey Khachatryan remedied that on Monday night. The young Armenian violinist — b. 1985 — appeared in Zankel Hall.

And he began with maybe the mightiest of all works for solo violin: the Chaconne from Bach’s Partita No. 2 in D minor. You hear this so often in transcription, it was almost a relief to hear it on its original instrument.

And Mr. Khachatryan did many things well in it: He was marked and resolute — undoubting. And he was ever attentive to the melodic line. But this was not exactly a spiritual experience. And Mr. Khachatryan had technical problems, to boot.

He was sometimes flat, sometimes fuzzy, sometimes rough. A squeak or two came out. And his sound was now and then sickly. Zankel Hall can be an unforgiving place, its acoustics all-exposing. By the way, the nearby subway trains seemed louder than ever. Nothing like a solo-violin work to make them deafening. I could not agree more with my colleague Fred Kirshnit: This situation is not “interesting” or “funky” or “cool” or “urban.” It’s a real shame.

After the Bach, Mr. Khachatryan played the Franck Sonata, joined by the pianist Lusine Khachatryan. Mother? Sister? Aunt? Sister — a couple of years older. She played the Franck with notable beauty of tone — pearly — and notable smoothness. She is not just the sister of a young star, but a musician in her own right.

Little Brother, unfortunately, committed some slow, slow tempos. Last summer, he played the Beethoven Concerto at the Mostly Mozart Festival at Lincoln Center, and I’m surprised the middle movement isn’t still going on. That was a bizarre experiment in stasis.

In Franck’s first movement, Mr. Khachatryan was so slow, so languid, he was funereal, simply killing off the music. It had no air, could not breathe. Also, he used so much portamento — did so much sliding around — I thought, “Gil Shaham would blush.”

In the second movement — marked Allegro — he was again slow. To be generous, you could say “deliberate” or “measured.” I would say slow, and painfully, ruinously slow. In the ensuing Recitativo-Fantasia, he was nicely ruminative, at the beginning. But limpness took over, and the music had no chance.

And how about that wonderful, much-cherished last movement, which brings a canon? Its tempo was almost — almost — reasonable. But the music still lacked its flow and joy and pleasure. I should say that Mr. Khachatryan phrased well, and that his dynamics were apt.

But there is something negative to say about Lusine Khachatryan: In loud, splashy portions of this movement, she played on top of the keys, rather than into them. This was her only poor playing of the night.

I might pause here for an “aw” moment: It was awfully good to see brother and sister playing together. Siblings have been doing this from time immemorial — since long before Wolfi and Nannerl (Mozart), and Felix and Fanny (Mendelssohn). The Khachatryans’ parents, who are both professional pianists, must be terribly proud.

After intermission, it was the Shostakovich Sonata, Op. 134. Mr. Khachatryan played the work with far more sense than he had the Franck. There was much less monkeying around, and far more persuasiveness. Mr. Khachatryan captured the fearful tension that comes with Shostakovich. In the middle section of the last movement, he was both earnest and edgy. And in the last section, he was duly bleak, mysterious. The music didn’t so much end as flutter off …

Incidentally: The page-turner turned pages for both pianist and violinist, shuttling between the two. In a lifetime of concertgoing, I don’t think I had ever seen this.

The Zankel Hall audience went nuts for the Khachatryans, and I suspect there were more than a few Armenian Americans there. Bouquets of flowers abounded. The siblings obliged with what amounted to a second concert: four encores, starting with Rachmaninoff’s “Vocalise.” The violinist did not quite have the beauty of sound to pull this off, but he played sincerely and thoughtfully. The pianist did, in fact, have the requisite beauty of sound.

And then something American: Gershwin’s “It Ain’t Necessarily So,” in the famous Heifetz arrangement. Mr. Khachatryan played this beautifully and soulfully. But, frankly, there was no sin in it. And Sportin’ Life would not have approved!

Should a duo named Khachatryan play some Khachaturian? Sure. They whipped off the “Saber Dance,” and it was exciting. But the sibs were not entirely together in this tricky piece. And they ended with Piazzolla’s “Café 1930,” which was slow, slow, slow. Beautiful, in a way, and enrapturing, in a way, but slow, slow, slow …

Are they still having coffee in that café?