On Tuesday night, Maestro Louis Langree led the Mostly Mozart Festival Orchestra in a program that was … well, mostly Mozart. There were two soloists, a pianist and a soprano. The pianist was Emanuel Ax, a ubiquitous presence on the New York scene, and, indeed, the international scene. The soprano was Emma Bell, a Brit who has a big career in Europe, but was making her U.S. debut.

Mr. Langree began with the overture to a Haydn opera. What, you’ve never seen a Haydn opera, or heard a Haydn overture? So it is with most people. This was the overture to “L’isola disabitata” (“The Desert Island”). It is a nifty curtain-raiser, either for the opera itself, or for a concert.

At the beginning was an orderly G minor. We heard the Langree traits of preparedness and purpose. The conductor allowed the right spaces between notes. Then we heard a vigorous B-flat major, although the orchestra sounded a bit muddy. Was Avery Fisher Hall’s new configuration responsible? People are always fretting about the acoustics of this hall; perhaps it’s just better for one and all to try to play well.

Eventually, Haydn offers a strange little minuet in G major – strange, that is, in its placement. The orchestra played it purely. Then they closed with a strong, exciting, precise G minor. The cohesiveness of this ensemble is remarkable. They don’t play like a summer band (no offense to summer bands).

Around Mr. Ax, there was a small drama. A couple of days before the concert, he fractured a rib. He therefore canceled the recital he was to play after the concert, in the Stanley H. Kaplan Penthouse. That was taken over by Jeremy Denk. But he kept the concerto gig.

And it’s a good thing he did, because he played beautifully. The concerto was Mozart’s No. 22 in E flat, K. 482. This is one of Mozart’s greatest – but then, we can say that about roughly half of them.

In the first movement, Mr. Ax was smooth and elegant. Virtually his only failing was to rush in his passagework; he rushed elsewhere as well. The pianist brought his own cadenza, and it was a fine one: plenty of bravura, a nice inventiveness. Once more, the orchestra was excellent. It was both taut and free. The parts were clearer here than in the Haydn, and if the horns had trouble, when don’t they?

Mr. Ax stated his initial music in the Andante simply and beautifully. Throughout, he was amply expressive, but always tasteful. His playing was well weighted, well accented. And the C-minor ending was snaky, surprising – effective.

The performers’ tempo in the closing movement was leisurely, and their mood genial. Again, there was an attractive Ax cadenza, which featured bell-like chords in the right hand. If Mr. Ax wants to perform like this, his ubiquity is entirely welcome.

Emma Bell sang a Mozart concert aria, “Ah, lo previdi … Ah, t’invola agl’occhi miei.” Actually, it is more like a scena, and a barn burner. The piece was written for the same Prague lady as “Bella mia fiamma … Resta, o cara,” which Renee Fleming had sung in Mostly Mozart’s gala opener five nights before. Ms. Bell proved herself smart, capable, and winning. Her sound was slightly dusky – if a soprano can be dusky – and a bit unfocused. But her technique was superb, allowing her to do whatever she wanted, musically. Correct intonation was especially appreciated, and Ms. Bell was unerring even in quick, wide intervals. Always present was an evenness of line. And Ms. Bell’s diction was decent.

She fully conveyed the drama of this aria. Personally, I could do with fewer faces, but most would not object. Ms. Bell had a splendid American debut, in a difficult piece, by a composer whose music is the ultimate test for singers. (Not only for singers, to be sure.) Mr. Langree and the orchestra were far from bystanders: They breathed with the singer, and provided their own excellence.

Ms. Bell et al. performed a brief encore. Indeed, this was maybe the briefest piece Mozart ever wrote: “Un moto di gioia.” Ms. Bell was somewhat heavy in it, and some of us prefer a more coquettish, or giddy, approach. But she was of course respectable.

The program closed with Mozart’s Symphony No. 35 in D major, K. 385, known as the “Haffner.” Mr. Langree and the orchestra had played this in the opening concert – but with the movements broken up. This was a Whitman’s Sampler of a concert. They were even better on Tuesday night, playing the symphony uninterruptedly. It was zesty, tasty – enjoyed (by the performers). Mr. Langree exhibited that combination of freedom and control. And the presto finale was pure D-major exultation.

At the opening concert, they repeated this movement – but not this time. Mr. Langree offered no encore, although the audience gave him the opportunity (by the duration of its applause – not that performers require that, unfortunately). Every performance on this evening was first-rate. Why can’t we have this all year round?