The slow movement of Mozart’s G-minor Quintet is as heartbreaking as any music I know. I have written about this music before – a couple of pages in the foreword to my book of this same name repeat an article from New York Magazine in the 1970s, which in turn regurgitates wisdom verbatim from the classrooms of David Boyden and Joe Kerman at UC-Berkeley in the 1950s. Hearing it again last Friday, wonderfully played by the Calder Quartet plus Paul Coletti’s second viola at Zipper Hall, I found myself reacting more strongly than ever before to the G-minor outcry that begins the next movement, the ensuing Arioso – Mozart’s refusal to let go of the agonies he has shared with us over the eight minutes of the previous movement – and I ended the evening aware that my years of adoration of this one Mozart revelation so far have been in no way adequate.

That movement remains unique. Just the subtlety in the range of its tone color makes it so, in demanding that its five instruments perform muted until that overpowering release, the single high D that proclaims major triumphant over minor. In schoolboy enthusiasm I once proclaimed that D my favorite note in all music, and friends came over and asked me to play it for them – the one note! That’s nonsense, of course; a note is only a note in context. And when Ben Jacobson played it on Friday, because of the way he and his four partners had gotten themselves into the context of that amazing entire work, that stupendous panorama of suffering and irony and, in its final movement, an almost insolent masque of resolution, that high D had once again become, indeed, my favorite of all notes, ever.

The Calders are really good. They play the classical repertory with elegance and respect, patience and genuine wit. Beethoven’s first “Razumovsky” was their other big work on Friday, and this, too, was treated exactly right: a big, loving performance full of the great rhythmic quirks of middle-period Beethoven. Better still, they let the stars come out and shine all over the slow movement. That movement is just the reverse of Mozart’s. Midway, it simply soars, skyward, and the great performances do nothing to control the captivating ecstasy, as this didn’t.

The concert was free, and Zipper Hall filled up quickly with an audience young and attentive. Nobody applauded between movements. Ten-or-so years ago I wrote with concern about the dying out, or at least the aging out, of the chamber music audience. Now we have the Calder playing classic repertory at the Colburn School and the Denali playing contemporary repertory at Jacaranda, both to big, supportive audiences.

Both quartets, as it happens, played one of the new-music landmark works within the last few days and did so handsomely: Ben Johnston’s 1984 set of variations on “Amazing Grace” that wanders off into microtones and just intonation and other harmonic and contrapuntal shenanigans. The old boy was in town for a few days, and the Denali played his piece for him at an invitational party. Then, by the time the Calders played it to begin their concert, Ben Johnston himself had already flown off to Germany for some other celebration.

ECSTASY: I spoke of ecstasy back there. Then there is the slow movement of Maurice Ravel’s Piano Concerto: a quietly unfolding lyric line for the piano alone, untroubled, utterly joyous. At a certain point, as if the most natural thing in the world, a flute joins in, then others. Nothing breaks the quiet, loving…yes, ecstasy. That’s the way Martha Argerich played it last week here. Sure, it was thrilling, the way those iron fingers of hers shot out and made ice sculptures out of Ravel’s rhythms in the outer movements , but it was that slow movement, where you began by listening and then, without noticing, you found yourself breathing in the rhythm of the music itself. Yannick Nezet-Séguin, Montreal-born, was the excellent conductor, and put over a mostly moving Shostakovich Fifth although I found his tempo changes in the last movement a little off-putting. I cherish a tape from Kurt Sanderling’s days here as guest conductor; he knew Shostakovich, and he knew what this music was supposed to signify, and his way makes better sense than anyone’s else I know.

This weekend’s Philharmonic conductor, replacing Yuri Temirkanoff, has been the 31-year-old, obscenely good-looking, circa nine-feet-tall, curly-topped Pablo Heras-Casado, whom I managed to miss at his Green Umbrella debut last December but won’t ever again; he’s terrific. His bio, which has him leading virtually every new-music, experimental-music and youth-oriented organization here and abroad, goes on for days; that document is breath-taking, and so is his work. He leads without baton, but also without the affectation that many hands-only conductors employ; he is eminently watchable. His Mendelssohn “Italian” was crisp, spirited, impulsive; his Mahler Fourth was beautifully balanced. The devastating orchestral climaxes in first and third movements, which can sit at the edge of trashiness in less careful performances, were nicely, intelligently arrived at. Kate Royal sang the childlike Knaben Wunderhorn verses of the final movement very beautifully indeed, not chirpingly as some do but with wonderment and humor as all should. She stood, would you believe, even taller than Señor Heras-Casado; quite the sight.