Michael Tilson Thomas and the San Francisco Symphony have made a partnership from playing with expectations, and this first of two Carnegie Hall concerts this season was yet another example of their craft.

In a programme of Beethoven, Copland, and Steven Mackey, perhaps the most amazing subversion here was that by far the most interesting performance came in a Mozart piano concerto. Not that MTT or the SFS had much to do with it. For Denk’s was pianism of such invention, so far removed from any preconceptions of how Mozart ought to sound, that it seemed like MTT had no real idea how to keep up. The orchestra played as if stunned, and so they ought: in the way Denk mocked grandeur without losing sight of the humanity at Mozart’s core, this was like walking into the Met to find a floor covered in whoopee cushions.

After an elegant (but harried) introduction from the orchestra, Denk instantly infused Mozart’s music with a personal twist so idiosyncratic and yet so utterly lacking in self-seriousness that it was impossible not to smile. No line was played the same way twice, indeed few were treated with the straightness indicated in the score. Teasing, playful phrasing, impudently ornamented throughout, is what one would least expect in this most brooding, symphonic of Mozart’s concertos – no. 25 in C major – but it’s what we got. As the first theme reappeared at the end of the development, I actually burst out laughing. I might have done in the cadenza, too, were Denk’s flights of furious unpredictability and stunning twists of harmony not so gripping in themselves.

The slow movement was no less impulsive, although here that got slightly in the way of narrative flow. There was none of the metaphysical serenity that you might hear in the great, older recordings, but in this Mozart as in recent Bach and Beethoven on this stage, Denk’s playing was so fresh, courageous in its chutzpah, that it was impossible not at least to be amused. And so it continued into the finale, which opened with a flourish, and in which no opportunity to provoke and ultimately to delight was missed. By the end it felt like Denk had just ripped the score up and had started improvising. It was deliciously tasteless, and all the better for it.

Perhaps Denk had picked up on a wider theme in the programme, based on the notes that accompanied Steven Mackey’s Eating Greens. Mackey’s piece is dedicated in spirit to a “tradition of American ‘crackpot inventors’”, to generations of Stateside composers who had “a healthy irreverence for the European masterpiece syndrome” that, to some extent, afflicts us all (and me not the least). Eating Greens is now two decades old but was receiving its first Carnegie performance, and it picks up on the imagery of a painting Mackey once bought to create a quirky piece just brief enough to make sense. A kind of concerto for orchestra, it is split into three parts (“Religion, Food, Art”, “loose ends”, and “Five Chords”) and seven sections within them (titles include “Waffling (sic)” and “The Title is Almost as Long as the Piece Itself”), each a Schumannesque miniature contributing to the whole. Church bells intrude at the beginning, the hum of a café drifts over the electronics, and wah-wah trumpets take pride of place. MTT described the piece in brief remarks as charting the story of a good night out, perhaps with drugs involved, finishing off with a toy harmonica asking what on earth you’ve been up to. If that’s a case, a few more hallucinogens might have been welcome: the propulsive dance rhythms at the piece’s core never got my feet tapping, although the SFS played with their customary precision.

Declarative from the outset and stridently confident thereafter, in his Symphonic Ode Copland airs some smacking dissonances, and he finds in its repeated scherzo-like sections a physicality that makes up for a distinct paucity of thematic ideas. Mahler hangs over the piece, whether in half-lit string passages or the weighty stacking of sounds at the end, and Stravinsky is a clear influence in its tricky metres. As ever with this brand of Americana, MTT drew as good a performance as could be wished for from his orchestra.

At least Copland benefited from a sense of drive lacking from the not exactly hochdramatisch Beethoven that opened the concert. Lucid, even pellucid, this was a risk-averse Leonore overture that sounded more like postprandial stroll than an all-consuming celebration and elaboration of freedom. When you’ve got Denk around, though, even Beethoven seems dull.