Late into Friday night, violinist Christian Tetzlaff appeared cabaret style at the Stanley H. Kaplan Penthouse. He brought with him a superb accompanist and three composers on the cutting edge.

One of these daring experimenters was Mozart. Mr. Tetzlaff chose two of the mature sonatas for violin and piano and quickly established his credentials as an insightful and inquisitive explorer of older scores.

The Sonata in B flat major, K. #454 — the “K” or Koechel catalogue number indicates the place on an historical calendar in which the piece was composed and ends in the low 600s — began with a flourish, pianist Shai Wosner riveting the attention of the sold-out crowd immediately. Mr. Tetzlaff plays with high intensity and is especially adept at separating each and every one of his notes. There is never any seamless transition — what devotees might label portamento but detractors would call slurring — from one tone to the next. This modern European is as aware of the spaces between the dots on the printed page as he is of the sounds themselves. I have found his somewhat forensic approach a poor fit for works such as the Tchaikovsky concerto or the three Brahms sonatas in the recent past, but for Mozart it is eminently satisfying.

Since Mr. Tetzlaff is in New York quite a lot — he will be traversing all of the Beethoven sonatas this season at the 92nd Street Y — the find of the evening was Mr. Wosner, who magically transformed his modern pianoforte into a late 18th-century fortepiano by keeping his feet off of the pedals and matching his partner in lapidary note definition. Both artists were masters of their instruments, Mr. Tetzlaff even turning pizzicato passages in the Sonata in G major (K. #379) into ukulele styled strums by holding his violin at waist level.

It is easy to confuse the composers Kurtag and Ligeti. Both were named Gyorgy, both born in the Transylvanian region of Romania, both were Jewish, and both crossed into Hungary to study music. But Kurtag is more of a miniaturist than Ligeti, and this evening, the Tetzlaff-Wosner duo — they were by now not soloist and accompanist but rather full partners — offered a thrilling performance of Kurtag’s “Tre Pezzi,” Op. 14c from 1979, giving the violinist the opportunity to intone at his spectral best, sometimes employing a mute to establish a quiet, transparent, transubstantiated world of sound. The Mostly Mozart brochure had promised Webern, but this substitution inhabited that same rarified, hallucinatory world of high altitude and thin air.

All ended with a lively and yet thoughtful account of the Sonata ofMauriceRavel. YehudiMenuhin used to tell the story of how he was taking a lesson in the Paris apartment of his teacher George Enesco when Ravel burst in with the ink still wet on the manuscript of this new piece and the two great men performed it through twice with robust enthusiasm (undoubtedly Enesco at a much higher level than the pianistically challenged composer). This was totally a new sound — fresh, vibrant, and a little scandalous. Messrs. Wosner and Tetzlaff dove deeply into its forbidden harmonies and rhythms, expertly applying subtly syncopated rubato as appropriate. Mr. Tetzlaff lowered his instrument to his belt once again and strummed it like Django Rhinehardt’s guitar for just the right touch of Le Jazz Hot, although the second movement, titled Blues, could have gone even farther down and dirtier.

I have a personal preference for this 10:30 time slot and wish that Lincoln Center would schedule it throughout the season. They did indeed try three concerts last fall and the one I attended was filled to capacity. It is a wonderful opportunity to hear some great music after dinner, with a glass of wine in a posh setting. A first-timer seated at my table on Friday commented that this was the only way to enjoy chamber music. I couldn’t agree more.

The highly energetic ensemble Zefiro should receive a citation from the Mostly Mozart Festival, as the group not only performed the late night concert on Saturday, but was back at the Walter Reade Theater for the Sunday morning affair. The group is a bit hard to describe; it’s somewhat of a combination of a wind band and the Flying Karamazov Brothers. For Sunday’s presentation the music was indeed mostly Mozart, but with a little Alfredo Bernardini thrown in.

Who? Well, Mr. Bernardini, along with oboist and bassoonist Paolo and Alberto Grazzi respectively, founded Zefiro in the 1980s. It exists in Italy in several different guises. For this American appearance, 12 wind instruments and one double bass formed what in Mozart’s day would have been called a “harmonie.”

The function of these small wind bands was to play the hit music of the day, primarily snippets from fresh operas. Every court had one, and that of Emperor Joseph II included the clarinet virtuoso Anton Stadler, close friend of Wolfgang and the dedicatee of arguably his greatest works, the clarinet quintet and concerto.

There were two coatracks set up on the empty stage and I was puzzled as to their function until the musicians emerged. The four horn players played natural instruments — all of Zefiro’s instruments are of the period variety — and needed a place to hang their various crooks (rounded pieces of tubing that, when attached to the horn, produce a new key). The resultant ensemble sound was raucous and just a shade out of tune — perfect for authentic Mozart.

True to the nature of the harmonie, the players presented two suites of music from two of Wolfgang’s operas. First came “The Marriage of Figaro,” which includes some of the most refreshing music in history. These 13 men positively vibrate with animation and could not resist some extracurricular activities. For the conclusion of “Non piu andrai,” the wind players marched in place, double bassist Giancarlo De Frenza recalling Woody Allen’s cellist in a marching band in “Take the Money and Run.” For “Se vuol ballare, signor Contino,” Mr. Bernardini’s oboe was sweetly doubled in the horn, and on each repetition of the syllable “si,” the notes became ever more comic, regressing in their satiric kinship with Mozart from the salacious to the scatological.

By the time he got to “Porgi amor,” Mr. Bernardini was ready to travel, and serenaded various female audience members up close and personal while intoning such heartrending music. The men roamed about the theater — I had a clarinetist sitting next to me for a while —involving the audience members quite expertly in their reindeer games.

All was not sweetness and light, however, for the mood turned darker (although none the less comedic) when the subject was Don Giovanni. Here the overture sounded positively sinister, a great number of notes required from the bassoons to replicate the original string parts. In “La ci darem la mano,” Mr. Bernardini was a coquettish Zerlina to the bassoonist’s Don, but the music suggested, as it does in the original, that she is actually the one more interested in consummating the seduction.

Since both operas are set in Spain, the Cervantean device of having the tunes of “The Marriage of Figaro” played within the score of Don Giovanni was especially effective at this latter day commedia dell’arte. Parenthetically, the band that the Don hires to play at his dinner party testifies to the ubiquity in Mozart’s time of the harmonie.

Scotching the vocal line in favor of instrumental absolutism only served to reinforce what incredibly beautiful music this is. All kidding aside — although this is difficult to do when Zefiro is in the room — this was exquisite music making.