In “A Late Quartet,” writer-director Yaron Ziberman attempts something quite sophisticated: an ensemble piece that mirrors in its dramatic turns the movements of the piece that the four main characters, members of a prestigious string quartet, are practicing for the opening recital of their twenty-sixth year together—Beethoven’s No. 14, Op. 131 (one of his last quartets). There are many excellent things in the film, not least the splendid performances of the four remarkable leads. Unfortunately, there are also some serious wrong notes.

The Fugue Quartet, as they’re called, consists of first violinist Daniel Lerner (Mark Ivanir), second violinist Robert Gelbart (Philip Seymour Hoffman) and his wife, violist Juliette (Catherine Keener), and the old man of the group, cellist Peter Mitchell (Christopher Walken). As excerpts from a documentary on them interspersed through the running-time explain, the four came together, at the urging of Lerner, while the younger three were studying at Juilliard, and he brought Mitchell, a faculty member who’d once been a member of a now-defunct quartet, on board as well.

But there are troubles as the Fugue begins rehearsals. Mitchell, a widower still grieving the loss of his wife (a singer), finds that his fingers won’t follow his brain’s direction, and is diagnosed with Parkinson’s. The effort to find a new cellist for the group—which leads to a genteel stand-off with a pianist played by Wallace Shawn, who’s asked to release a player from his trio—leads to Robert suggesting that he and Daniel should alternate in first and second chairs. That causes friction not only within the group but between Robert and Juliette after her failure to support his wishes takes him into the arms of one of his jogging partners.

But that turns out to be the least of their problems. When Daniel takes up with the Gelbarts’ daughter Alexandra (Imogen Poots)—who’s studying violin with him—Robert’s fury is unbounded. The turmoil threatens to destroy the group entirely, as well as—even more tragically—some fine violins.

The ensemble of “A Late Quartet” is extraordinary in two respects. One is, of course, in the acting. The rigid Ivanir is convincing as the perfectionist Russian David, and Hoffman equally so as the more passionate, risk-taking Robert, while Keener makes a solid bridge between them. But the linchpin—as in many actual quartets—is the cellist, whom Walken underplays beautifully, shedding his usually over-the-top persona for something quieter, gentler, and deeply poignant.

But the four also excel in persuading that they’re real musicians. Their bowing and fingering are exceptionally convincing—a rarity in films about instrumentalists—and though extended passages are actually performed by the Brentano Quartet, who”dub” the actors, the effect is surprisingly sound, if you’ll pardon the pun.

The film does stumble, however, on the dramatic side. The whole Daniel-Alexandra plot thread is overdrawn, leading to a couple of unfortunate scenes—one in which the girl confronts her mother about having felt abandoned while she was growing up, and another in which she and Daniel have an assignation in her apartment and Juliette shows up, leading to his fleeing onto the fire escape. A sequence like that would be cliched even in a dumb comedy, but when it occurs in a film as serious as this, you know things have gone badly awry. (It doesn’t help matters that Poots can’t keep up with her co-stars, coming across as broad and obvious.) Similarly, the big finale—in which a changing of the guard occurs in the middle of the quartet’s premiere concert—is a contrived, unbelievable attempt to tag a Hollywood ending onto what’s overall an anti-studio sort of picture. The Beethoven Op. 131 certainly contains some highly charged passages, but they’re always controlled and powerful, not bombastic.

Still, despite its flaws, the fine ensemble and wealth of exquisitely played moments in “A Late Quartet” make for a cinematic concert with more ups than downs.