When Emanuel Ax was a 15-year-old Juilliard student from Israel, he was photographed by and featured in an article in National Geographic magazine. Essentially, he has never left since those days. Now a Juilliard faculty member, he used an opportunity Tuesday night at a Mostly Mozart Festival late-night concert to showcase one of his own students.The passing of the torch, the conviviality, the informality, the river view — everything was splendid about this night except the performance.

Mr. Ax was simply not at the top of his game. Of course, he has exemplary technique — that masculine touch, so clear and steady, coupled with an almost obsessive desire to exit notes as quickly as possible, makes his playing remarkably lucid. This program was not the most filigreed in the 18th-century repertoire, but it was still a pleasure to experience Emanuel Ax executing a trill with a mathematician’s sense of uniformity.

However, the outer movements of Mozart’s Sonata in D major, K. 311, which opened the proceedings, were not imbued with any measurable degree of élan.Rather, their rendition seemed oddly pedestrian, not Ax-handled at all. He did fashion an intricate and unhurried Andante con espressione in the middle and balanced this tempo very well with the pace of the other movements — a fact that shouldn’t have to be stated, but have you heard many Classical period performances lately?

Mr. Ax, quoting from an unnamed book on pianism, called the Rondo in A minor “sensuously elegiac.” This is an apt description of the piece, but not, regrettably, of its present realization. I wished for much more of a singing line throughout, much more emotive weight — even a little rubato would have gone a long way. It just seemed that Mr. Ax was not focused this night. Perhaps the late-night concert was past his bedtime.

The student in question was Orion Weiss, a Bachauer winner and former member of Chamber Music Society Two, the triple-A team at Alice Tully. Mr. Weiss exhibited much more driving energy than his mentor, and a steely-fingered staccato technique in Mozart’s Sonata for Four Hands in C major. Mr. Ax rather self-effacingly took the bottom part to allow his discovery to shine. But it appeared Mr. Weiss needed more time to study this work, as, even with the printed music in front of him, he committed a couple of major gaffes.

And structurally and stylistically, this selection is very similar to the opening sonata. If you are going to perform a Mozart recital at a Mozart festival in a Mozart year, then a little variety is in order. The net effect of this long-winded collaboration was just a bit tedious.

Jocularly acknowledging his fatigue, Mr. Ax yielded the stage to Mr. Weiss for a rather matter-of-fact reading of “The Girl with the Flaxen Hair” by Claude Debussy. This piece was owned by Heifetz back in the day, but Tuesday night’s was indeed the original version for solo keyboard. Mr. Weiss was spot-on in terms of accuracy, but neglected to caress the loveliness of the poetry, producing instead a mechanical, if flawless, version.

And what did they do for an encore? Why, what everyone does, the G minor Slavonic Dance of Dvorák!

Tuesday’s concert proved Mr. Weiss has more to learn from his mentor. Butthere was a time in Mr. Ax’s career when he was still a few years away from the pinnacle of his profession. Mr. Weiss has a good chance to make it to the top as well.

Until August 26 (Lincoln Center, 212-721-6500).