WASHINGTON (AP) — Early in the second act of Donizetti's opera "Anna Bolena," the heroine confronts her lady-in-waiting Jane Seymour, who confesses that she will soon replace her as the wife of Henry VIII.

It's one of the great scenes in bel canto opera. And as performed by soprano Sondra Radvanovsky and mezzo-soprano Sonia Ganassi at the Washington National Opera on Tuesday night, it exploded off the stage and sent sparks flying into the auditorium at the Kennedy Center.

It was the unmistakable high point of an evening that, despite a good deal of fine singing, otherwise never quite caught fire.

Part of the problem was the visually imposing but heavy-handed staging by Stephen Lawless, part of it the limp conducting by Antonello Allemandi.

And then there was Radvanovsky herself. This prodigiously gifted American soprano remains something of a work in progress.

There was a lot to like in her first crack at this touchstone role, which the legendary Maria Callas restored to the modern repertory in 1957. The basic quality of Radvanovsky's voice can be thrilling — a penetrating sound that is hard-edged without being harsh. She unleashed astonishing power, especially at the top of her range (though she was not always able to scale back the volume when she should have). But there were still traces of her tendency to sing flat, and some of her phrasing was rhythmically imprecise.

Dramatically, she has not yet found the emotional depth to portray the tragic queen as much more than the weepy victim of a conniving king. The one exception came in the encounter with Ganassi, when the Italian mezzo's own intensity seemed to jump-start her performance. Throughout the night, Ganassi used her ample, plummy voice to create an impassioned portrayal of a woman torn between her love for Henry and her pity for Anna.

American bass Owen Gradus made a handsome, swaggering Henry, binge-eating and drinking as he engineered the trap that would rid him of his unwanted wife. He sang energetically, though his voice is a size too small for the role. Georgian tenor Shalva Mukeria displayed a pleasant, slightly nasal sound and nailed his many high notes as Anna's beloved Percy. British mezzo Claudia Huckle was impressive in the trousers role of the hapless page Smeton.

The production, created for the Dallas Opera, uses a single set by Benoit Dugardyn consisting of large wooden panels that surround the stage and take different configurations as scenes change. Scenery is wheeled in or lowered from the flies. Choristers appear on two tiers of balconies above the walls. This allows for some striking tableaux as the figures overhead watch and comment on the action below.

But Lawless has a way of belaboring the obvious, including his overuse of Anna's daughter, the young girl who would become Queen Elizabeth — and figure prominently in two subsequent Donizetti operas. The real Elizabeth was not yet 3 when Anna died and has no role in the opera as written. Played here as a girl of about 10, she is dragged into numerous scenes to witness her mother's degradation, even watching as Anna puts her head on the chopping block at the end. In a program note, Lawless speculates this may be why Elizabeth never married!

There were other miscues, like the pantomime during the overture that showed Henry shedding one wife for the next, played incongruously for laughs. And it was a mistake to drop a large grill with prison bars during Anna's final scene, obscuring our view of her just when we should be focusing our eyes on nothing else.

The production, which opened the company's season Saturday night, runs for six more performances through Oct. 6. For Radvanovsky, it's a warm-up for an even more demanding assignment: In coming seasons she will repeat the role at the Metropolitan Opera and will add the heroines of Donizetti's two other "queen" operas — "Maria Stuarda" and "Roberto Devereaux."