BLUE HILL – The Brentano String Quartet is named for Antonie Brentano, believed by many to be the subject of Beethoven’s letter to his “Immortal Beloved.” This letter symbolizes deeply felt passion that was eventually kept hidden. While the quartet certainly feels the passion, fortunately, they do not keep it to themselves.

On Sunday, the quartet, consisting of Mark Steinberg

and Serena Canin on violin, Misha Amory on viola, and Nina Maria Lee on cello, launched the Blue Hill Concert Association’s winter concert series. They began with Mozart’s “String Quartet No. 19 in C Major,” K. 465. The piece is known as the “Dissonance Quartet,” and it posed the question of the day: What is dissonance?

The “Dissonance Quartet” is one of the six “Haydn Quartets,” so named because Mozart dedicated them to Joseph Haydn in gratitude for all that he had learned from the older composer. These quartets generally are known for being concentrated music, with nothing transitional or filling about any of the passages, and this seemed to connect with a last-minute change in the program as well as the question of the day.

The beginning of the first movement contains the cross relations that caused the “Dissonance.” A cross relation is a chromatic passing tone that occurs not in the same voice but in another one.

Cross relations are “against the rules,” but one definition of genius is someone who not only knows the rules, but knows how to bend or break them. At any rate, here in the 21st century, these seem perfectly innocent.

The remainder of the first movement served fair warning that Brentano’s Mozart has muscle and passion. There seemed to be occasional and minor problems with pitch, and sometimes the cello voice seemed to fade into the rest, but toward the end, everything was in balance and even the realities of a Maine audience in winter did nothing to distract from the music.

There was a brief tuning and then, in the spirit of the Italian heritage in Mozart’s training, the instruments seemed to sing during the second movement, and this was as well sung as any I’ve heard in person. The emotion poured into this music made every sound in the building appear to be a part of the song, even sounds that are part of the spice of a live performance. Once, an overtone hung in the air after a phrase and, instead of sounding like a mistake, it seemed as if a string were saying, “Wait, I’m not done with what I wanted to say.”

The third movement (Menuetto) lived up to its marking, as the quartet seemed literally to be dancing with its body language. It was elegant fun, with cellist Lee at one point seeming to ask Amory on viola if she could cut in. The allegro of the fourth movement was exuberant fun as well, and really showed Brentano’s vision of Mozart, sometimes playing near the line of exaggeration in phrasing and tempi, in ways that are not often associated with Mozart, but are the essence of live performance.

The quartet then made an inspired change to the program and inserted Webern’s “Six Bagatelles.” A bagatelle usually is a minor piece for solo piano – Beethoven excluded – but these Webern pieces are anything but trifling and present challenges in performance that are not often overcome. Violinist Mark Steinberg said they were intended as a juxtaposition with the pieces to follow, but they also seemed to fit with Mozart and showed once again that Brentano is not afraid to take a chance.

Webern’s is the music of abstraction, and Steinberg quoted them as “moments that flash before our eyes, captured in the air just long enough for us to have a glimpse of them.”

This abstraction can seem quite dissonant, with each individual note seeming to have more of a relationship to silence than to another note.

Not here. Bretano presented the music in a manner that might have offended Webern traditionalists, but presented it with such heartfelt clarity that at the end I had to apologize to the poor woman in front of me for my, er, percussive enthusiasm.

The first part of the concert concluded with “Smoke Fragments”, by Steven Mackey. These pieces were inspired by Webern’s work, and show Mackey’s willingness to use any and all sounds that are possible to produce with an instrument. Mackey hoped that, because of their brevity, the listener could “momentarily savor, in memory, the entire shape of the piece, like a smoke wreath before it evanesces.”

Delicate rings they are, especially the final one that seemed to be drop of a bit of ash from a coal. The note hung in the air for a second, and then applause came like a fire roaring to life once more before intermission.

Bartok’s “Quartet No. 1, Op. 7” comprised the second half of the concert, and if anything was meant for the Brentano way, it was this piece. The opening movement works through a series of fierce attacks and climaxes in which there still was something slightly held back. Particularly fine was the viola line with cello support as the music progressed. There was a slight faltering in a passage that moved from the viola and cello through the violins but, again, no matter. While hitting all the notes properly certainly is a goal, live performance isn’t always about perfection. Sometimes, it’s about hearing something for the first time.

At one point, the violin relentlessly hammers at a note, and in this performance it seemed as if the violin were pounding at something, getting slightly tired but refusing to give up until finally, briefly, everyone joined.

I’ve never heard it in exactly that way before. And in the final moments of the piece, the strengths of the Brentano quartet all were revealed in a combination of technique and ensemble work with ferocious energy and a willingness to take chances. By this point, absolutely nothing was held back.

Some listeners may take issue with this approach, asking that the music be allowed to speak more for itself. What I will remember is feeling that, even though Brentano was at the other end of a full room, I felt Bartok’s notes swirling all around me in a dance of heat that got me through the rest of a raw, cold afternoon. I also will remember that the question of the day was answered in the negative: whatever dissonance is, it’s not this.

The Blue Hill Chamber Concerts will continue at the Congregational Church of Blue Hill on Feb. 11 and 25, and March 4 and 11, at 3 p.m.