Almost a year after it started, András Schiff’s Bach project in New York is finally coming to its conclusion. He began on the Upper East Side, at 92Y, with both books of The Well-Tempered Clavier. His performance of Book I, I wrote, was “of the highest quality and depth of thought”. Hurricane Sandy split the two concerts, and after the waters subsided Schiff was on more monastic form for Book II, in a recital that “felt just plain wrong, almost voyeuristic” in its “purgative, deeply personal flavor”. The complete English Suites followed at Lincoln Center, as well as a a concert of concertos with the New York Philharmonic, and a mammoth evening of the French Suite, the Overture in the French Style, and the entire Italian Concerto as an encore. And so, at last, to Carnegie Hall, and the six Partitas.

Schiff has been performing the Partitas as a group for many years now, and indeed a recording, his second of these works, appeared in 2009. These concerts are tremendous feats of stamina, and this one lasted for nearly three hours. He rearranges the ordering to perform them out of sequence, but in a way that makes sense. Performing them not 1-2-3-4-5-6 but 5-3-1-2-4-6, with an interval after the Second, not only provides a satisfying rise through the keys (G-A minor-B flat-C minor-D-E minor), but allows the two more exercise-like works to pass as preparation for the intimacy of the often overlooked First. More impressively, everything builds up in a natural emotional progression, ending the first half with the terrorising Second, and pairing the two largest works, the Fourth and Sixth, to make a satisfying denouement.

Schiff used to be a very idiosyncratic player of Bach, although given how particular these works are to each and any pianist, idiosyncracy is even more subjective a judgment than usual. Schiff’s skills in this music are immense, the product of a lifetime’s devotion to the composer and a complexity and intensity of lateral thinking about not just his piano works, but his whole oeuvre. Famously, Schiff dares not touch the sustaining pedal in Bach – except for one note in one of the books of The Well-Tempered Clavier. Usually that does not matter, and it has the benefits of clarity and rigour, as well as allowing an appreciation of Schiff’s natural facility of touch. Even more here than in his concerts of the suites, this Bach was freely ornamented too, so much so that it became difficult to distinguish between the incidental, the ornamental, and the fundamental. That, nevertheless, is the point of trills and turns, and Schiff delights with the unexpected: experimentation and interpretation are one. Question is, when does the unexpected simply become mannered or eccentric?

In the Second Partita, as it turned out. More than in perhaps any other piece, Bach here seems to look directly to Beethoven, and not just because it is impossible to associate C minor with anyone else. It’s a coiled spring, tensile from its tripartite opening Sinfonia, finally snapping by the end. Bach here is at his purest, his most concise, and one longed for Schiff simply to play things straight, with a steely thread. Fairy dust sprinkled the Courante, though, and the Sinfonia tended towards the delicate. Particularly perplexing was Schiff’s urge to pull the tempo around arbitrarily, shifting the accents around in the Sarabande, and bending time unnecessarily in the febrile closing Capriccio.

The same traits threatened to mar the Sixth, too, but they were contained to a bizarre boogie-woogie interruption in the Gigue, which also had its momentum held back by snatchy phrasing. Elsewhere in that mammoth work, though, Schiff was at his very best. The Toccata brooded with its dense chromatic harmonies, ornaments and drama brought together as it circled implacably. The Corrente bubbled as if in some Ravelian tone-poem, while the crushingly solitary Sarabande agonised over what seemed to be a hellish void.

The Fourth was floridly magical as well, insatiable in the drive of its fugal Ouverture, half covering the tension of its Allemande with breezy phrasing, and galloping with filigree fingering in the Courante. Its Sarabande was perhaps the highlight of the concert, childlike in its simplicity yet wise in its grace.

The lesser-known works came off particularly well. The opening Fifth was dexterous, deliciously coy in its Sarabande, bouncy in its Passepied, theatrical and witty in its cross-handed Menuet. The Third was more constrained, troubled even, but the First was especially fine. The poise of its opening Praeludium recalled the The Well-Tempered Clavier, while its Sarabande flowed with a lonely regality, and its Gigue maintained a fleet balance.

Throughout, Schiff benefitted for a well prepared Steinway, something that cannot often be said even at Carnegie Hall: due praise ought to go to his technician. Schiff moves on to his final concert next week, pairing the Goldberg Variations with Beethoven’s Diabelli Variations.