Daniel Barenboim enjoys one of the biggest careers in music. He was a boy pianist, became a conductor, and remained a pianist. Even as he has gone from podium to podium, he has concertized, and recorded, at the keyboard.

Moreover, he is an intellectual, one of the great talkers about music in the business. In this, he is like James Levine, another pianist-conductor. Mr. Barenboim has a phenomenal ability to articulate what he knows. Indeed, sometimes it is better to read Mr. Barenboim on music than to hear him in it.

As a pianist, Mr. Barenboim likes the Big Gesture, the Project, the Happening. For instance, he likes to play the complete Beethoven sonatas, as he did at Carnegie Hall two seasons ago, over eight recitals. And, to the same hall on Monday night, he brought Book I of Bach’s “Well-Tempered Clavier.” All of it.

Should all of those preludes and fugues be played at one sitting? Is that what Bach intended, or desired? Is it musically satisfying? Is it wise? Each can answer for himself, but what seems to be important to Mr. Barenboim is the Event. A couple of preludes and fugues at the beginning of a recital; a Mozart sonata; some Brahms; some Ravel; some tangos – boring, or at least conventional. Something complete – now we’re talkin’!

Everyone likes to be all musicological these days; it is one of the baneful trends in music. Performers are applauded for their purity, as though they were teachers or curators, rather than performers.

About “The Well-Tempered Clavier,” I could go on forever – we all could – but I will confine myself to a few words. It may be the central tablet in music. Perhaps the best thing Beethoven’s teacher in Bonn did for him was place “The Well-Tempered Clavier” in his hands. It sank into his bones, and brain, serving him for the rest of his life.

And we remember Pablo Casals, who, as an old, gnarled man, began each morning with a prelude and fugue at the piano. It aided him physically, mentally – in every way. It was a form of prayer, really.

As for Mr. Barenboim, he recently recorded Book I, and could thus avail himself of all the tricks of the studio. But, two nights ago at Carnegie, he faced the music, so to speak. It was not pretty.

The C-major Prelude is probably the purest of the bunch. And Mr. Barenboim played it admirably – freely and pianistically, but admirably. This pianist takes full advantage of that instrument, not trying to imitate a harpsichord or anything else. And yet a certain unevenness of rhythm was disquieting. The C-major Fugue, he played almost like a Chopin nocturne: That’s how free it was. Fine, but Mr. Barenboim also jabbed at the keyboard when he wanted to emphasize something, which was completely unnecessary. Suggestiveness will do.

In the C-minor Prelude, we could see that technical facility would be a problem. (Where does this peripatetic musician find time to practice, anyway?) He was sluggish, muddled, thick-fingered. Mr. Barenboim likes the big, fat tone, learned from one of his idols, Arthur Rubinstein. And that tone can be very useful to a pianist. But in every fleet piece, Mr. Barenboim was in trouble.

The C-minor Fugue was full of strange accents, distorting the line, and it was also big, big, like Beethoven. What’s more, Mr. Barenboim held the final note for an absurdly long time. He would do this repeatedly, especially after a fugue: He would keep his foot on the pedal while using both hands to turn the pages of his music to the next piece. (Had I mentioned that Mr. Barenboim had the book on his rack?)

I will stop with particulars in a moment, but let me keep going for a second.

The C-sharp-major Fugue is a perfect piece (aren’t they all?), and it is also a fairly simple one, technically. But it was simply beyond Mr. Barenboim’s present capacity, and he panicked in it. You could hear the panic in the notes, as Mr. Barenboim flailed and made mush. He used a lot of pedal throughout the evening, but this was not entirely a matter of musical choice: It was in part to (attempt to) cover a technical inability.

The C-sharp-minor Prelude, he played exquisitely. It was haunting and beautiful. But the Fugue, he pounded. Why? How could that be justified? The Fugue was as big as the “Hammerklavier” Sonata, with the emphasis on “Hammer.” Over and over, Mr. Barenboim played far too obviously, as if his listeners were stupid, as if he had to say to them, “This is a very important voice,” or,”This is a very important harmonic moment.” He seemed afraid of subtlety – as though we wouldn’t get it.

The D-major Prelude was uncrisp and uneven; Mr. Barenboim (again) made a hash of a simple piece. And the opening of the Fugue was representative: He pounded the first note, then rushed the rest. Worse, however, was the pounding of the opening note in the E-flat-major Prelude – it was well-nigh criminal. It was hard to sit in one’s seat.

I will address one more coupling, briefly: The E-major Prelude was shapely and graceful – a relief, frankly. But then the pianist had to go and sock it to the Fugue, vulgarly.

Let no one fool you: There is not One True Way to play Bach, including “The Well-Tempered Clavier.” Bach is accommodating (to a point). Edwin Fischer, Glenn Gould, Rosalyn Tureck, Andras Schiff – all of these pianists have had something to say, and that’s leaving aside the harpsichordists. Absolutism in Bach is ill advised. Wanda Landowska was witty when she said, “You play Bach your way, and I’ll play Bach his way” – but she was obnoxious, too. No one has a pipeline to the master.

Still, there are limits – limits of taste and conception and interpretation. In my view, Mr. Barenboim transgressed those limits, and did so with lousy technique. Talented eccentrics can persuade; Mr. Barenboim did not persuade, or at least did not persuade me.

Of course, he can do pretty much what he wants in the concert world. The big venues – including the biggest, Carnegie – will give him his head, apparently. If he wanted to play tiddlywinks onstage for two hours, concertgoers would show up, and cheer lustily. But Monday night was a bad outing for this great musician. He is better than he demonstrated, and so is Bach.