Kate Lindsey and Randall Bills in the Washington Concert Opera's “La favorite.” (Don Lassell/Don Lassell)

Donizetti’s “La favorite,” as the original French version of the opera is known, takes a while to warm up. At least it did on Friday night, when the Washington Concert Opera brought it to Lisner Auditorium. Act I trundled along with an array of arias that simply aren’t top-drawer. But once Alphonse, the king, and Léonor, his mistress (the “favorite” of the title), squared off in a duet, the evening began to strike sparks — thanks to Javier Arrey, an ardent and warm baritone as Alphonse, and the marvelous Kate Lindsey, who made the most she could of a role that arguably was a less perfect fit for her voice than the Romeo she sang in Bellini’s “I Capuleti e i Montecchi” a couple of years ago.

Whether sung in French or Italian, the lead role of this opera is usually a vehicle for a big dramatic voice — Dolora Zajick, for instance, has made it her own. Lindsey doesn’t have that kind of voice. What she does have is a sound of dark beauty that she uses with dramatic intelligence, and WCO apparently, and smartly, chose to cast the opera to her scale, with lighter voices.

Opposite Lindsey was the Fernand of Randall Bills, a young tenor who’s the very model of a high-strung lyric tenor, nervous as a racehorse with a lovely, clean, light sound that was a little too dry, a little too tired by the end to hit the center of the bull’s eye. Still, he was often a pleasure to hear and well embodied the impetuous naivete of a monastery-novice-turned-military-hero who follows a beautiful unknown woman into marriage only to discover he has dishonored himself. (The idea that marrying someone else’s former mistress automatically brings dishonor makes this a hard opera for stage directors to update to the modern age.)

Balthazar, Fernand’s superior in the monastery, was sung by John Relyea, who over the years has grown into a kind of gravitas and impression of substance that used to elude him; he’s still a bit generic, but there’s a warmth and content to the voice that’s very welcome. And the soprano Joélle Harvey made a lovely impression in the requisite confidante role of Inès.

If Act I seemed slow, it was in part because Antony Walker, the WCO’s music director, seemed to be missing some of his signature spring; the orchestra sounded a little mushy. As good bel canto performances will, the evening gradually built a head of steam as the performers fed off one another’s energy. Certainly the climax was Lindsey’s delivery of the opera’s showpiece aria, “O mon Fernand,” showing her musical intelligence as she marshaled her resources and found her own way into a scene that tempts one to over-sing at every turn and can easily shred a lighter voice. She sang it gorgeously and brought down the house. But she was a cool presence onstage; time and again, it was Arrey who gave the warmth.

The Washington Concert Opera’s 30th season, in 2016-17, will include an anniversary concert as well as Massenet’s “Herodiade,” with Michael Fabiano and Joyce El-Khoury, and Beethoven’s “Leonore,” with Marjorie Owens. dcconcertopera.org.