THEATRE / It's only a part of love: The word is that 'Passion', the new Sondheim musical, marks a departure. Robert Cushman saw it in New York

STEPHEN SONDHEIM has frequently been criticised for not writing songs that say 'I love you' straight out. This seems to me more of a virtue than a vice, especially when you consider the recent musicals that have fallen over themselves to say it, usually in the most bloated, generalised and pseudo-poetic terms. In treating the subject urbanely, circuitously, or obliquely, Sondheim has been following an older and nobler Broadway tradition.

Anyway he has written plenty of touching romantic songs, though admittedly they have tended to do with love misprized, misplaced, or simply missed. His new show Passion, which has just opened on Broadway, is, as both its title and advance publicity suggested, the nearest he has got to a direct take on love reciprocated and attained. If taken as a definitive statement on the subject it's frightening, and more than a little suspect. Passion and love may overlap, but they are not the same thing. As a study of a special case it's convincing and compelling.

The case in question is Fosca, a 19th-century Italian woman who is sickly - dying, in fact - and ugly. She is also intelligent, shameless, infuriating, a moral and emotional blackmailer. Her prey is Giorgio, a handsome young army officer whom we first meet in bed with his equally presentable married mistress, assuring one another that nobody in the world has ever loved as they do, or words and notes to that effect. By the end this affair has proved too conventional to stand up under pressure, most of it applied by Fosca. At curtain-fall Giorgio is singing a different love-song: Sondheim at his most fastidiously stark. Fosca's obsessive-possessive devotion has, finally and painfully, awakened a corresponding devotion in him.

Passion is based on a film by the Italian director Ettore Scola, itself derived from a novel. One can see why it attracted Sondheim. Obsession is one of his themes. Think of Mama Rose in Gypsy, Seurat in Sunday in the Park with George, Sweeney Todd, the entire cast of Assassins - most of them, come to think of it, sexy and capable of inspiring love though not too good at returning it. Mostly, they turn their lovers off. Fosca turns hers on by turning him off; in the show's most brilliant number she dictates to Giorgio, from her sickbed, the love- letter she would like him to write and he, torn between pity and embarrassment, complies.

That sounds horribly funny. So does the idea of Giorgio, bouncing between his two flames and getting increasingly scorched. So does Giorgio embracing the love of his life, while knowing she is under effective sentence of death. But that is all in the story, not in the treatment. Apart from some perfunctory writing for Giorgio's brother officers, there is less humour here than in any other Sondheim score.

I regret that, but I think I can see the reason. I have to do some guessing here, not having seen the movie, but people who have describe it as a black farce, with Fosca an outright grotesque. The adaptor-writer James Lapine (Sondheim's collaborator on Sunday in the Park and Into the Woods) has softened and humanised it. Donna Murphy, the stunning young actress-singer who plays Fosca, is something new in Broadway divas: she makes her most powerful points quietly. Her voice encompasses dark cello notes that alternately soothe and disturb; her presence is a standing, or reclining, rebuke to the comparatively happy or healthy people around her. She is plain and severe, but she is not hideous; if she were a female Phantom of the Opera or Hunchback of Notre-Dame it would actually be easier.

We could feel sorry and dismiss her, as if she were a fairy-tale. The show allows us to resent her manipulations, but it asks us to believe in her and respect her. And, while the music is playing, we do.

Giorgio has more work but less opportunity; the show is actually his journey but in Jere Shea's performance he emerges as little more than a hard-pressed juvenile lead with a good voice. Lapine's staging, minimalist by current Broadway standards but lavish by most others, uses spare suggestive sets that only hit trouble towards the end when they have to run rather hard to keep up with the story; his dialogue, of which there is a good deal, is admirably functional. The show is a favourite to win the Tony Awards for new musical (the only real competition is the Disney stage version of Beauty and the Beast, which has some thematic similarities), so Broadway audiences, and London audiences later, should have some time to respond to its demands. These are not unprecedentedly harsh but they are unusual; girl, in a manner of speaking, gets boy, and we are challenged to feel good about it. I would hate to think that Sondheim and Lapine feel that this is all there is to say about love, but it makes a stimulating interim report.

Plymouth Theater, 236 W 45 St, New York (0101 212 239 6200): Mon-Sat 8pm, mats Wed & Sat 2pm.

(Photograph omitted)