The greatest musical theater stars can be so multifaceted in their talents, or so adroit at particular skills, that their pure acting chops are sometimes underappreciated. When one thinks of Kelli O’Hara, say, the first qualities that likely come to mind are a sterling soprano voice and a glowing presence. With Brian d’Arcy James, also a fine singer, there’s the comedic facility that has distinguished his performances in shows such as “Something Rotten!” and “Shrek the Musical.”

Both performers, of course, have repeatedly proven their capacity for challenging drama, in musicals and straight plays alike, dating back to the adaptation of “Sweet Smell of Success” that first paired them on stage more than 20 years ago. The new Broadway production that now brings them together again is another dark musical based on a classic film, “Days of Wine and Roses”; under Michael Greif’s vigorous, compassionate direction, it proves, if not a flawless work, a superior showcase for their extraordinary gifts.

First produced off-Broadway last year, “Days” also marks Ms. O’Hara’s reunion with composer/lyricist Adam Guettel and librettist Craig Lucas, the team behind “The Light in the Piazza,” which secured her stature as a leading ingénue. Nearly two decades later, the actress retains the kind of wholesome pulchritude that helped make a 20-something Lee Remick so devastating in the role Ms. O’Hara plays here: that of Kirsten Arnesen, a practical and self-sufficient young woman who becomes half of an alcoholic couple on a downward spiral.

Mr. d’Arcy James is cast as the other half, Joe Clay — Jack Lemmon’s role onscreen — a public relations exec driven to drink at least in part, one suspects, by his experiences serving in the Korean War (the show, like the movie, is set just after our withdrawal) and the often ethically questionable demands of his job. Although Kirsten is a teetotaler when they meet, and succeeds in giving up booze for substantial periods after they marry and have a daughter, her addiction eventually proves even more stubborn and destructive than that of her husband. 

In Kirsten, Messrs. Guettel and Lucas have given Ms. O’Hara a role as challenging as Hamlet; and unlike Shakespeare’s Danish prince, her character is required to sing 14 songs: half of them alone, many of them virtually operatic both in musical structure and emotional scope. Mr. Guettel’s sharply dissonant score — anyone unfamiliar with his previous work would certainly never guess he’s the grandson of Richard Rodgers — also incorporates elements of jazz and blues, and its metallic quality can make Ms. O’Hara’s normally lustrous vocals sound shrill.

Yet there is transcendent warmth in Ms. O’Hara’s performance, the most nuanced and wrenching I have ever seen her give. Mr. d’Arcy James manages his own vocally and dramatically daunting part with similar aplomb, and the stars sustain a pulsing chemistry throughout, in their bleakest moments as well as the funnier and sexier ones the show’s creators and director mercifully provide.

Granted, “Days,” like the film that inspired it, is not long on comic relief; even the neon signs that flash in Lizzie Clachan’s set — indicating various shops and destinations, prominent among them a wine store and bars — serve more to reinforce the ominous tone than to suggest rays of light. Where the show felt like a chamber musical downtown, Mr. Greif and his designers and cast ensure that its urgency fills a bigger house without sacrificing empathy.

The company also includes Byron Jennings, characteristically unfussy and gripping as Kirsten’s concerned father, and an endearing David Jennings as the sympathetic but tough-minded sponsor who helps Joe get sober. Young Tabitha Lawing makes a delicately stirring Broadway debut as Joe and Kirsten’s 7-year-old daughter, Lila, who must assume responsibility for her own well-being while watching her parents self-destruct.

Yet there is hope in “Days.” In a song called “Forgiveness” and its reprise, Joe and Kirsten respectively express both regret and resolve: “I can teach others now/Teach them what I know,” Joe sings, after getting on the wagon; Lila, though not quite there yet, yearns for the same, and asks herself, “What am I afraid of? Is it living?”

We’re reminded in moments like this, throughout the show, that the best musical theater singers are also marvelous actors. If you won’t leave the theater humming Mr. Guettel’s tunes, you will walk out with a renewed appreciation of its leading man and lady.