Is it an insult to a quartet to say that it was at its best accompanying? I hope not, because in a program of rare quality throughout, it was in Respighi's Il Tramonto that the Borromeo Qt. was most remarkable. The piece is a setting of Shelley in Italian translation, and is normally sung by mezzos (though the singer here was the fine baritone Christòpheren Nomura). The idiom is is a heady mixture of Puccini and Strauss that seems naturally to demand a stage and an orchestra in the pit. And the quartet met its part of that demand magnificently. I don't mean the loud, passionate passages, which any good quartet would have handled well, but the quiet ones, where four players have to phrase together with the balance and delicacy of an orchestral string section playing pianissimo. Never have I heard that illusion carried out so well as it was Saturday night — the lines smooth and serene and rising and falling as one. Done by sixty players it would have been great orchestral playing; done by four it was a near-miracle.

Both here and in the concert-opening Barber Dover Beach (where the quartet put the same skills to like use) Nomura was superb — sonorous and passionate and articulate. Given that his reputation has been built largely on Baroque and Classical music, it was a treat to hear him, so to speak, so far from home, and evidently enjoying himself so much.

Between the two vocal works came Steven Mackey's Ars Moriendi (2000), which I gather was written for the Borromeos. It's an extraordinary piece, a sort of mingled chronicle and remembrance of Mackey's father's death, bound together by a sort of representation of the dying man's breathing. It's like the "breathing" motif in Britten's Nocturne, but much slower and more painful, and with an anguished "wheeze" from the second violin (using what string players call a "practice mute" — a metal device attached to the bridge of the instrument that leaves only a tinny remnant of the original sound). Other motifs come and go over the course of nine short movements, including some antic dance-like music that positively throbs with joy. But there are crises, and the "breathing" motif comes back again and again. And finally there comes a point where the "Londonderry Air" arrives, fragmented almost beyond recognition amid the painful breaths, and when it is over the violins evaporate upwards and the music is done.

It's hard even to describe such a piece without at least raising the suspicion that it was cheap or exploitative; I can only say that it didn't seem so to me.

After the Mackey and then the Respighi, Beethoven's Op. 130 Quartet (complete with Grosse Fuge) seemed almost anticlimactic, though the performance was terrific — virtuosic, but not self-consciously so, and full of little poetic touches. Here at last, too, it was possible to hear the players in full flight on familiar ground. What an interesting quartet this is! The outer players (Nicholas Kitchen, first violin, and Yeesun Kim, cello), have the more penetrating sounds, but the inner players (William Fedkenheuer, second violin, and Mai Motobuchi, viola), with their mellower tones, are every bit as strong and even more active.

I'm not certain that that isn't the best possible makeup of a string quartet. It certainly made for fine Beethoven. The best things were the set-pieces — the scampering second-movement Presto, the just-a-little-off-kilter "Alla tedesca," and the Cavatina, where anyone who hadn't yet internalized the quality of Fedkenheuer's violin playing would finally have gotten the point. As for the Grosse Fuge,it was at once enthusiastic almost to the point of hysteria (Motobuchi, I'll swear, spent more time out of her chair than in it) and fiendishly controlled. Which is really the only possible way to play the thing. A Grand Finale to a remarkable recital.