For the last concert of her Perspectives series at Carnegie Hall, Renée Fleming assembled one of the least coherent concept programmes imaginable. Billed as “Vienna: Window to Modernity”, it was never clear what was specifically Viennese about the music on show, nor what was particularly modern, nor what windows had to do with anything. If this was about the fin de siècle and the turbulent culture that accompanied the collapse of the Austrian empire, then historians are going to have to redefine what a siècle might be, let alone a fin. Fleming presented pieces written between 1857 and 1938: that is, from two decades before Brahms finished his First Symphony to four years after Arnold Schoenberg’s emigration to the United States. What Brahms’ naïve Ophelia-Lieder and Wagner’s Wesendonck-Lieder had to do with Viennese modernity, I have no idea.

It was a good thing, then, that Fleming had assembled outstanding musicians to accompany her. To see pianist Jeremy Denk padding across the stage in his velvet jacket is always a guarantee of thoughtful and stimulating pianism. And although it was not billed that way, this was actually the final Carnegie Hall appearance of the original Emerson String Quartet: in less than a week, cellist David Finckel moves on to other things. (How charming that he turned Denk’s pages!) Alas, with Fleming’s earnest monologues and the instrumentalists’ awkward entries, everything sadly felt rather cobbled together.

A pity, really, for there was some outstanding music-making on show. Joined by violist Paul Neubauer and cellist Colin Carr, the Emersons managed to bring out the Brahmsian influences on the (original) string sextet version of Schoenberg’s Verklärte Nacht, to a degree very rarely heard. Again and again this performance seemed underheated until one realised that it was structure rather than outright passion that was the musical aim, shrouding Schoenberg’s realisation of Richard Dehmel’s risqué poem in frostiness and almost symphonic process. Sumptuously played, it felt like a performance straight out of the salon, restrained, almost alienated, as if the heat of the piece needed to be kept at a distance for fear of what it might do to the listener.

Hearing Verklärte is never something to complain about, although this might have been a great opportunity to hear Schoenberg’s Second String Quartet, which features a soprano part in full late-Romantic vein. Still, Fleming and the Emersons more than made up for that omission with a searing performance of Webern’s Drei Stücke, which are brief meditations on the death of the composer’s mother. Fleming showed marvellous voice control and attention to the myriad nuances of sound that are thrown into Webern’s curt text, while the Emersons’ Romantic treatment of their part amply showed how fine the line was between Schoenberg’s early work and the dissonance he and his followers would soon emancipate.

We began, though, with two versions of Ophelia’s songs from the fifth act of Hamlet. Richard Strauss’ trio benefited from Denk’s eerily disfigured playing in “Wie erkenn’ ich mein Treulieb”, and his Rosenkavailer-on-opium approach to “Guten Morgen, ’s ist Sankt Valentinstag” and “Sie trugen ihn auf der Bahre bloss”. Fleming took a little time to warm up – she found her most fulsome Strauss voice for a later encore – but when not under pressure she beautifully melded musical line and textual precision. Brahms’ five, folksy versions of these songs were given in Aribert Reimann’s arrangement for string quartet, and here Fleming oddly found it difficult to project. However, “Und kommt er nicht mer zurück?”, the closing prayer, was magically hushed.

The difference between Brahms and Strauss is of course Wagner, and Fleming opted for the very rare string sextet version of his studies for Tristan to open the second half. “Im Treibhaus” was too matter-of-fact, but “Träume”, which looks forward to the great Act II love duet, was outstanding, so intimate that one could almost imagine Wagner fantasising about Mathilde Wesendonck singing it for him. Fleming also sang two of Schoenberg’s cabaret songs with gusto, as well as two less memorable ditties with string quartet from Karl Weigl, one Stravinskian number from Egon Wellesz, and three songs by Eric Zeisl. Zeisl’s “Komm, süsser Tod”, written just before the composer departed Vienna, was hauntingly done.

For me, though, the highlights were two of Brahms’ Op. 118 Klavierstücke, played ideally by Denk. They might not be terribly “modern”, but Denk still made the first sound completely of a piece with Verklärte Nacht (or at least the Verklärte heard here). And he brought just the right balance of poignancy, resignation, and confidence to the second piece, singing its melancholy with nuanced rubato, polyphonic lines, and a comforting sense of return in conclusion. It goes without saying that Denk also brought his uncommon panache to his accompaniments of Fleming, particularly in the cabaret numbers.

The encores were Strauss’ “Morgen”, with Eugune Druckner on violin, a spot of Korngold, and, of all things, “I’m in love with Vienna”, from The Great Waltz.