There was quite a bit of excitement in the lobby of Jazz at Lincoln Center on Thursday evening, as two celebrities — Neeme Jarvi and Derek Jeter — were on hand at the same time. Mr. Jeter was making a personal appearance, while Mr. Jarvi was entering the Rose Theater to hear his son Paavo conduct at the Mostly Mozart Festival.

Paavo Jarvi has done wonders as music director of the Cincinnati Symphony Orchestra and takes the reins of the Orchestre de Paris in 2010. He is also the head of the Deutsche Kammerphilharmonie Bremen, a small ensemble numbering about 40 players at any given time that can be considered the authoritative Beethoven orchestra of our day, and is resident at the Beethovenfest in the composer’s birthplace of Bonn.

Mr. Jarvi wasted little time in establishing a “wow” effect at this all-Beethoven affair. The opening chord of the Creatures of Prometheus Overture was spectacular, the combination of such supple playing and the slightly reverberant acoustics of the small theater immediately arresting. It was remarkable to hear such a full string sound from such a small ensemble and whenever the long-bore trumpets and timpani, played with hard sticks, joined the proceedings, the resultant tutti was magnificent.

Argentinian pianist Ingrid Fliter was on hand to perform and Mr. Jarvi and his troops were also playing, but it was difficult to imagine that they were indeed all reading from the same score the Piano Concerto No. 1 in C Major The orchestra was precise and muscular, classically balanced and nuanced When Ms. Fliter entered, however, she intoned in a sweetly Romantic style at a much more relaxed tempo. I’m no purist, so I was with her all of the way, even though her style of play was at least 40 years away when Beethoven first penned this concerto. Mr. Jarvi, though appeared not to be in sync with her slight rubatos and elongated passagework, and this caused problems.

The first two movements were haunted by this legitimate disagreement, but the Rondo simply got away from Ms. Fliter. Mr. Jeter would have been able to empathize. You can perform a play perfectly 100 times in a row during practice, only to flub it in front of the fans. I’m sure that Ms. Fliter will produce many very good performances of this piece in the future.

But all was swept away by a stunning realization of the Symphony No. 7. It is difficult to imagine a more exciting traversal of this most exciting of the nine symphonies. Mr. Jarvi had his team perform the entire piece without pause, so that the triumph of the ending of the Vivace, with its horns hitting those cruel high notes flawlessly, was immediately supplanted by the solemnity of the famous Allegretto, one of the most moving depictions of human suffering from any art form in cultural history.

Yes, I’m aware of the composer’s tempo markings, but this movement really only reaches its height — or is it depth? — of emotion at a slower pace. It is no longer fashionable to perform this essay deliberately, although this was the norm for most of the last century. Few modern conductors — Daniel Barenboim is one of them — still wring every last drop of blood, sweat, and tears from it, and that’s a shame. But at least Mr. Jarvi was on the slower side of the Allegretto designation.

The final two movements were electrifying, with the players reaching such a high level of energy and commitment that they were positively vibrating in their chairs. No American orchestra past its student years would ever dare to dig into a piece so enthusiastically and never sacrifice one iota of precision. Except for an old von Karajan recording, I can’t remember a performance so thrilling.

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With their numerical designations reversed, symphonies five and six of Ludwig van Beethoven made their premieres at the same monster concert in Vienna in 1808 in which Beethoven threw in everything but the kitchen sink. On Saturday at Avery Fisher Hall, the Mostly Mozart Festival Orchestra recreated this event as two separate concerts. If they had truly desired to replicate the original, though, they would have had to perform much less competently.

This current ensemble is quite technically adept and has a decent sound for what is essentially a pickup orchestra. Maestro Louis Langree opened the afternoon concert with a relaxed version of Beethoven’s “Pastorale.” To be sure, there were some less-than-perfect passages, a poorly articulated horn solo in the third movement, and a falling off of inner string sounds in the oddest of places, but these are but cavils. Overall, the performances were quite pleasant.

But that was the problem. Mr. Langree sashayed around the podium while his troupes kept up a steady barcarolle, comforting and prettified, but never profound. The scene by a brook was particularly dull. This was Beethoven on a perfectly even keel — even the storm was docile. Only at the conclusion, when the music finally caught up with the interpretation, did all seem to gel. If there had been a recording of this performance, listeners might have enjoyed it, but few would feel the need to add it to their collection.

Soprano Anja Kampe had difficulties with the concert aria Ah! perfido, with virtually every attempt at a loud or high note resulting in sharpness and shrillness. But vocal order was restored with the appearance of the Swedish Radio Choir for the Gloria section of the Mass in C Major (remember, this was Beethoven’s original tasting menu). Here the orchestra seemed to dig in a little deeper and the singers were immediately impressive and invested. Beethoven injected a sense of the fugal into this movement and the choir gave the cum Sancto Spiritu section quite a wild ride. Their zaftig aggregate sound bodes well for their major appearance on Tuesday night in the magnificent Requiem of Gabriel Faure. Tenor Philippe Castagner was an eloquent soloist.

Besides the two symphonies presented that fabled evening, the composer also took the opportunity to introduce the Viennese public to his Piano Concerto No. 4. Jeffrey Kahane is probably best known not as a pianist but rather as the conductor of the fine Los Angeles Chamber Orchestra. This evening, he produced a confident keyboard effort, marred a bit by his tendency to blur runs on a consistent basis, but always interpretively interesting. In its accompaniment, the ensemble sounded suitably dark and ominous as appropriate, the very qualities that were absent in the opening symphonic performance.

Most impressive was the Andante con moto, into which Mr. Kahane poured a great deal of emotive power. Had the outer movements been more finely chiseled, this could have been a superb realization.

There is much divergence of critical opinion in this town, and that is a good thing, but one statement with which all we reviewers can agree is that the Mostly Mozart Festival Orchestra sounds much better than it did five years ago.