When a character named Vincent van Gogh opens his mouth and begins to sing, you can be pretty certain that what comes out won't be "Whistle a Happy Tune." No, a number for a bona fide tortured genius -- mutilated ear and all -- has to plie and jete rather unpredictably up and down the musical scale, has to twist anxiously, rise skittishly, alight on odd notes. It has to sound a little off and a lot like pain.

This the composer Michael John LaChiusa accomplishes in spades in "The Highest Yellow," his cerebral, inventive and ever so earnestly arty new musical. The show, directed in its world premiere at Signature Theatre by Eric Schaeffer, is in part an attempt to find an urgent musical vocabulary for ecstasy, to help us understand a visionary artist's desperate need to follow his rapture, "the highest yellow / where I know no fear / where I disappear / from my life."

As performed in the buff, in a bathtub, on a mental ward, by Marc Kudisch, this song -- a mini aria, actually -- unfolds with an ever more breath-catching approximation of bliss. Kudisch, Tony-nominated for "Thoroughly Modern Millie" and seen last season on Broadway as the barker in the revival of Stephen Sondheim's "Assassins," makes for a vocally explosive van Gogh, a man who by dint of expansive imagination and dangerous self-destructiveness earns the right to sing in the key of suffering.

The excitement Kudisch generates in the part is a valuable commodity, because little else in this noble effort musters anything like it. LaChiusa -- creator of such art-house musicals as "Marie Christine," a modernized "Medea" and "The Wild Party," which sets to music the Jazz Age poem of the same title -- does not have a problem conveying emotion in his compositions; although often written in tight rhymes, they express feeling in a cascading, stream-of-consciousness sort of way. The difficulty arises in the undifferentiated manner in which the characters sing to themselves and to one another. In "The Highest Yellow," the sense of a cast of seven performing in one voice traps the enterprise in an all-too-uniform emotional orbit.

Vocal technique is so central here, in fact, that "The Highest Yellow" feels closer to opera than to musical theater; were it not for the nonpareil skills of the leads, the show would be very difficult to endure. As it is, the production, enhanced by Jonathan Tunick's vibrant orchestrations and the full-bodied sound of a 10-piece orchestra conducted by Jon Kalbfleisch, fills Signature's space rousingly. It offers pleasing accompaniment for the three principals, welcome guests from Broadway: Kudisch, the dashing Jason Danieley and an actress you might describe as a songbird for the thinking person, Judy Kuhn.

They are the legs of "Highest Yellow's" improbable love triangle, as imagined by LaChiusa and the book's writer, John Strand. The musical is set in 1888, in the hospital in Arles to which van Gogh was taken after he cut off his ear in a brothel in homage to a prostitute, played here by Kuhn. (Van Gogh killed himself two years later, at age 37.) The artist, of course, figures prominently in the plot, and his witty introduction comes as he is wheeled onto Walt Spangler's grimly antiseptic, white-tiled set, his head swathed in bloody bandages. Over him, a hard-bitten nurse (Donna Migliaccio) sings, "You chop off your ear / You're going to bleed."

LaChiusa is greatly influenced by Sondheim, but despite chords that hint otherwise, this is not the macabre lair of "Sweeney Todd" or the turbulent garret of "Sunday in the Park With George." And it isn't even really van Gogh's musical, either. Center stage is held here by the impressionable young doctor assigned to treat the artist, Danieley's Felix Rey, who in fact was painted by van Gogh, in a famous portrait now owned by a museum in Moscow.

The musical's conceit is that the easily influenced Rey, a naif in love with van Gogh's prostitute, conspires to prevent the artist's release, at first out of devotion to him and later to keep him away from Kuhn's Rachel. The deeper source of Rey's jealousy toward van Gogh, the show suggests, is a sort of passion gap, the idea that van Gogh's ecstatic if tormented embrace of his art allows him some secret communion with the mysteries of the cosmos. Rey's futile ambitions -- the yearning of an ordinary man to be extraordinary -- lead him on a path that almost destroys the more important man.

The romantic triangle is a means by which LaChiusa and Strand also explore the notion of obsession, and how, when in the grips of one, life is both more painful and more interesting. In one of the musical's most engaging -- and Sondheimian -- songs, Danieley and Kuhn perform a duet about their mutual fixation on van Gogh, through the concept of contrast. "You need the dark to make the light lighter," Kuhn sings. "You need the touch of sun next to the gray." Van Gogh is both the darkness and the sun in "The Highest Yellow" -- and the only reason we care anything about these other, grayer people.

The sublime, sad-eyed Kuhn is not ideally cast as an earthy Provencal call girl; her allure on a stage is of a more refined caliber. Danieley is a better fit as the callow Rey, who's so obtuse he believes that Rachel is smitten with him, even after the humiliating act of forking over several francs following a night of lovemaking. Even so, the book puts the actor at a disadvantage; he's asked to make some fairly acrobatic leaps over logical chasms in the script. Aside from a mention early in the story that Rey is a virgin, Danieley is given no moment to explain what feels like a linchpin of the story, an ardor that will drive him to the edge of madness.

A more entrenched problem has to do with the deployment of a "Sweeney Todd"-style chorus of hospital patients (Migliaccio, Stephen Gregory Smith and R. Scott Thompson) who serve as both quasi-narrators and mirrors for the thoughts of van Gogh. Schaeffer, whose staging of the intimate scenes involving the three major characters is always lucid, seems less sure how he wants to utilize these malleable figures. On a narrow, elongated stage framed by a pair of imposing doorways -- the entire show appears to be taking place in a chilly hallway -- they seem to be three characters in search of a purpose.

Daniel MacLean Wagner supplies elegant mood lighting in -- surprise! -- deep yellow, and costume designer Anne Kennedy's frills and fur for Kuhn and Migliaccio (who also plays a rather stern-looking madam) relieve, for an instant or two, the production's general gloom. Come to think of it, there is no levity to speak of in "The Highest Yellow." This deficit is cause for nothing as drastic as the cutting off of an ear. But those expecting a less astringent evening might find themselves wanting to tear out a hair or two.

The Highest Yellow, music and lyrics by Michael John LaChiusa; book by John Strand. Directed by Eric Schaeffer. Set, Walt Spangler; costumes, Anne Kennedy; lighting, Daniel MacLean Wagner; orchestrations, Jonathan Tunick; sound, Tony Angelini; musical direction, Jon Kalbfleisch. With Harry A. Winter. Approximately two hours. Through Dec. 12 at Signature Theatre, 3806 S. Four Mile Run Dr., Arlington. Call 800-955-5566 or visit www.signature-theatre.org.

Judy Kuhn and Jason Danieley are two sides of the triangle in "Yellow."As a vocally explosive Vincent van Gogh, Marc Kudisch generates much-needed emotional excitement.