Well, that was something that I, for one, had never seen before: the Jimmy and Danny Show. On Monday night at Carnegie Hall, two giants of our musical times shared the stage: James Levine and Daniel Barenboim. Each is a pianist and conductor. Each is a formidable musical intellectual. But they have taken slightly different career paths: For one thing, Mr. Barenboim plays the piano more.

And that’s what he did on Monday night. He was soloist in a Boston Symphony Orchestra concert, conducted by Mr. Levine. The program consisted of Schoenberg and Beethoven (in that order). And it began with Mr. Levine himself — together with his orchestra, I should say.

They played Schoenberg’s “Verklärte Nacht,” or “Transfigured Night.” Mr. Levine is a good conductor of this piece (as is Mr. Barenboim, incidentally). In some hands, it can be intolerably soupy and syrupy, but Mr. Levine injects sense and rigor. He also knows how to pace the work. This is a piece that needs to build properly, sort of like Rachmaninoff’s “Isle of the Dead” (and many other compositions).

On this occasion, the BSO displayed a rough, rather grainy sound. This was especially true in the early pages of the work.Mr. Levine was not going for an elegant “Verklärte Nacht,” evidently — and certainly not a superficial one. The piece is more than beautiful.

Yet there were grounds for complaint. Flatness plagued the strings — and this is a string-only piece — throughout.This affected solo players as well as the orchestra collectively. And some entrances were poor.Also, the piece simply demanded more beauty at times. When the music bloomed with D major, where was the warmth? And Schoenberg’s shimmering bits could have been far more shimmering. Like his teacher Zemlinsky — and other Zemlinsky students — Schoenberg sprinkles fairy dust. But here it was a little pebbly.

“Verklärte Nacht” was written in 1899. By the time Schoenberg composed his Piano Concerto, he was a different composer. The year was 1942. And it was to this piece — seldom heard — that Mr. Barenboim sat down.

The opening bars, he played beautifully and dreamily, with that big, fat, Rubinsteinian tone of his. Unlike Rubinstein, however, he tends to pound out a melody. Why he does this is a mystery. He doesn’t conduct that way: He doesn’t have a violin section, for example, mar a melody with wrong and harsh accents. Again, a mystery.

The athletic, muscular parts of Schoenberg’s score, Mr. Barenboim tended to play well. Few are better than Mr. Barenboim at muscularity — you should hear his Bartók First. All through the Schoenberg, the pianist laid on a lot of pedal, somewhat cheating. But that was forgivable.Mr. Barenboim kind of brazened out this piece — he does that, often.

Unfortunately, the two giants — Messrs. Barenboim and Levine (three, if you count the BSO) — were not together much of the time. You can bet that this was not the conductor’s fault. And, interestingly, Mr. Barenboim used a score, turning his own pages. That was a neat trick, although it was no friend to musical flow.

Mr. Barenboim was not through with his evening’s work. After intermission, he played another concerto, Beethoven’s Fourth, in G major. Now, Mr. Barenboim is a very curious Beethoven player (as he is a curious pianist all around). Four seasons ago, he played the Beethoven sonatas — complete, all 32 — in Carnegie Hall. Some of them were absolutely first-class.And some of them were so bad, you would not think a conservatory reject capable of such awfulness. And these highs and lows could occur on the same evening.

The first thing to say about the Beethoven Fourth on Monday night was that Mr. Levine conducted it superbly. The phrasing, the rhythm, the sheer life — all were awe-inspiring. Almost never do you hear Beethoven conducting at this level, and Mr. Levine proved himself once again the heir to George Szell (under whom he worked, long ago).

As for Mr. Barenboim, he rushed and slopped through the first movement — rushing, slopping, rushing, slopping. Mr. Levine had no chance to be with him; he could only wait to be alone. In addition, Mr. Barenboim made up a few notes of his own (and not bad ones!). He played the cadenza thoughtfully and appealingly. Part of it felt a little Latin American, I swear.

Mr. Levine conducted the orchestral statements of the slow movement with titanic power. In his responses, Mr. Barenboim did not provide true soft playing, but faked — disembodied — soft playing. Also, he was far too flabby in his rhythm. He played the closing Rondo with unquestioned gusto, but, like the first movement, it was largely a slopfest. Not entirely, however: Mr. Barenboim executed some runs, up and down, like a real pianist.

Speaking of real pianism: The audience applauded and applauded, and Mr. Barenboim finally obliged with an encore. It was a Schubert Impromptu, one in A flat (D. 935, No. 2). And, my heaven, it was wonderful — sublime. It could have been Backhaus at his golden peak. Was this the pianist who had played the concertos?

What a weird evening.