Daniel Barenboim comes out on stage at Carnegie Hall, where he's presenting an eight-concert cycle of all the Beethoven piano sonatas, and space seems to curve itself around him. He knows that he's a consummate professional, and -- since he's not just a pianist, but one of the world's most powerful conductors -- also a celebrity. He brushes off applause. He doesn't need it; he's just here to play.
In person, too, he's formidable. Argentine originally, Israeli now, music director in Chicago and Berlin, a man whose eyes weigh everything they see, he talks and listens just the way he plays, with apparently unshakable confidence. I'd been asked if I wanted to write about his Beethoven, and I thought it would be interesting to move away from all the usual generalities, and concentrate instead on the concrete details -- the thinking every musician needs to do to translate Beethoven's written notes into deep, communicative music. So I wondered if he'd talk to me about a single Beethoven sonata, and through his publicist he'd told me to pick any that I liked. I chose a quiet one, the "Pastorale," identified among musicians as opus 28; it's understated, peaceful and full of yearning details.

I asked Mr. Barenboim how he played the beginning of the piece, which breathes itself into existence, with no announcement, fuss, or introduction. "The difficulty about playing the beginning of this," Mr. Barenboim pronounced, "is that you have to play it as if it was already going on. As if you were joining the train." Then later, with more poetry: "I try to hear in my inner ear the sound as if it had been going on for an eternity."
Is that easy? "Yes," he said, without a sign of even momentary doubt. He also offered some philosophy: "Music is much more about becoming than about being. I agree with you that the beginning of the first sonata is being, the statement, not becoming. But the sense of becoming, of evolution, is at the beginning of all sound."

When he spoke like this, he'd sound as if he'd said these things a hundred times before; that often happens, when people talk a lot in public, or to interviewers. And when I heard the second of his Carnegie performances -- they began on June 9, and continue through June 26 -- I noticed that he plays as if he'd played it all before, unfolding each sonata as if he knows exactly where it's going to go. But his certainty is powerful, and he can also breathe out glowing, gripping, quiet sounds. And even when he fills the hall with personality that won't allow for contradiction, he also comes alive within each moment, listening with sharp attention to everything he plays.
Toward the end of the first movement of the sonata, just for instance, there's a note that Beethoven seems to stretch out, in the printed music. But Mr. Barenboim doesn't hold the note for very long. I asked him why. "You are playing the note," he answered, "as the continuation of the chord before. And only after you have played it, and played it very softly, then you strike the chord in the left hand, and the note becomes transformed. Then you wait as long as the sound can hold. This is not something that you count, six or nine or 12 or four beats. Instead you listen to what the sound does in the room."
Sometimes he hesitated, searching for a thought; he can speak in every major western language, and I'm sure in Hebrew, but to me his English wasn't always quite at ease. "I hold it less," he said, again about the pause, "because I want to create the connection with the next note. And therefore if I would wait long, it would have no connection."

That led to something that I'd never thought of. Beethoven seems to stretch the note with a mark called a "fermata," which means, supposedly -- ask any music student -- that the note is very long. But Mr. Barenboim says no: "I feel that Beethoven writes the fermata to show you only that the notes are out of time." Or, in other words, that you simply play the music freely; these are the leaps you have to make to bring a printed score alive. We went step by step through much of this sonata; Mr. Barenboim had definite opinions everywhere. Such certainty, I'll say again, is audible in his performances, though at the cost, I think, of any feeling of surprise.
He laughed when I said that I don't like the sonata's final movement. I told him that I find the music somewhat fragmentary. Nor, I ventured, did I agree with Mr. Barenboim's 1998 recording of it, on which he takes great care to shape each fragment. I'd rather see him push the music faster, as it's played by Artur Schnabel, a pianist of the past revered, perhaps too much, for his profundity. "I spoke very often about Schnabel with [Claudio] Arrau," Mr. Barenboim came back at me (Arrau was another great pianist, from the more recent past). "And he said Schnabel by the time he recorded the Beethoven sonatas was less in control than he had been, and this is why he plays very fast sometimes and hurriedly."
Which is to say that Mr. Barenboim knows more than anybody, though, to be fair, he also very seriously explained more reasons why he disagreed with me. I wish I were free to hear him play the "Pastorale" on June 22 at Carnegie. He's formidable, as I've said -- and has enough finesse to prove he might be right.