This season promises to be a breakout year for Joshua Bell. While he plans to continue performing as a soloist in Romantic works, in which he is nonpareil, he will also venture into two other areas. Some in his fan base are especially excited that he is taking up conducting, as this will afford them the opportunity of viewing him from behind for an entire evening. He is also going back to his roots to play chamber music, which he did Sunday afternoon as part of the Mostly Mozart Festival.

The concert, titled “Joshua Bell and Friends,” may be the beginning of a series, as Mr. Bell has agreed to be a friend to cellist Steven Isserlis in two evenings at Zankel Hall in December. For this current effort, he invited the fine Miro Quartet and a posse of the usual suspects from his generation for a program concentrating on youth.

Even had I never encountered the Piano Quartet in G Minor, K. 478 before this Mozart year, I would be by now an expert in its intricacies. This was approximately the 10th iteration that I have heard since New Year’s Day. Mr. Bell teamed with pianist Frederic Chiu, Miro violist John Largess, and cellist Edward Arron, perhaps best known around town as the director of the Metropolitan Museum’s Artists in Concert series. Their reading was deliciously politically incorrect, with Mr. Bell’s inborn romantic nature sculpting the phrasing in mid-19th-century style. Mr. Chiu was especially unMozartean, confidently intoning his lusty piano part as if he was performing Brahms. No lily-livered periodicity for this group — this realization brought out the underlying passion that always bubbles just beneath the surface in these ostensibly polite Enlightenment works. This was not Mozart playing for purists. I loved it.

And the audience did too. Mr. Bell always draws a younger crowd, and this group rewarded the presentation of the first movement Allegro with a hearty ovation, richly deserved. This was truly Mr. Bell’s concert.

For better or worse, crossover has played a large part in Mr. Bell’s phenomenal success. He and Mr. Chiu met bassist Edgar Meyer at Indiana University, and this afternoon they unveiled his Concert Piece for Violin and Piano just a few days after their world premiere performance in California.Mr. Meyer is a frequent partner of Mr. Bell in the arcane art of bluegrass music, and perhaps this is the reason the violinist felt the need to introduce the work with some comments. However, his statement that “Edgar Meyer belongs with Mozart and Mendelssohn” may have been protesting just a tad too much.

The work itself was not without merit, the opening labyrinthine, the third movement unwrapping an unhurried and lovely melody. But the group offered not only the obligatory perpetuum mobile, allowing the soloist to strut his stuff, but a second, concluding section also consisting of non-stop bowing, albeit of the Riverdance variety. This emphasis on pop effects cheapened the experience, but the paying customers seemed to love it.

Finally, Mr. Bell tried his hand at one of the most glorious youthful compositions in the repertoire, Felix Mendelssohn’s Octet, written when the composer was all of 16. Adopting the double quartet approach, he stationed the Miro group on one side and placed himself and his gang (Colin Jacobsen, violin; Nicholas Cords, viola; and Mr. Arron, cello) on the other. This platform positioning proved unfortunate, as it pointed out the rather obvious difference between a group that plays together all of the time and what was essentially a pick-up ensemble of sidemen.

What should have been a gentle, delicate, lighter-than-air rendition turned into a rather muddy and ponderous experience. Mr. Bell was still in his romantic groove, which would have been fine, except that his three quartet mates had not received the memo. Phrasing decisions were not at all uniform: When the cello, and then the viola, and then the violin repeated the same snippet of melody, it was as if they were performing from three different scores. Meanwhile, the Miro foursome (Daniel Ching and Sandy Yamamoto, violins; Mr. Largess, viola; and Joshua Gindele, cello) was blissfully in sync, providing a much more pleasant undercarriage than what was going on to their immediate right. Let’s hope that this is not a portent of Mr. Bell’s conducting to come. He might just lose a few friends.