Washington Concert Opera including Kate Lindsey, left, and Nicole Cabell, center, with Maestro Antony Walker at GWU Lisner Auditorium. (Don Lassell)

The Wolf Trap Opera deserves a lot of credit. This is not, to be clear, a review of a Wolf Trap production. The show I saw on Sunday, Bellini’s “I Capuleti e i Montecchi” (a.k.a. “Romeo and Juliet”), was presented by the Washington Concert Opera, and an engrossing, melodious presentation it was. But two of its brightest lights have sung leading roles in this region. David Portillo, a tenor, and Kate Lindsey, a luminous mezzo-soprano, each spent two summers at the Wolf Trap company, which identifies and supports young talent. (Lindsey, from Richmond, was back at Wolf Trap for an intriguing recital in 2011.) Audiences may not have been quite prepared for just how great they were going to sound a few years down the line.

“Capuleti” is, arguably, not vintage Bellini — by which I mean that it lacks the distinctive melodic profile of, say, “I Puritani,” and that a lot of the melodies tend to evoke other, more assertive melodies from his other operas. (The opening of the duet “Vieni, ah vieni in me riposa” from “Capuleti” gets another and perhaps better attempt in the “Puritani” duet “Vieni fra queste bracchia,” to name one of many examples.) Its story, too, is a bit slender; it’s based on the same sources as Shakespeare’s play, rather than on Shakespeare itself, and involves only five characters, including a rather small role for Friar Lawrence (here named Lorenzo, sketchily sung by the bass Liam Moran).

On the other hand, Bellini left so few operas that one tends to treasure every bit of music that he left. And his melodic gift was so abundant that “Capuleti” offers plenty of good listening — especially when it’s as well sung as it was Sunday. The very first aria comes from the tenor, who here has an auxiliary role as Tebaldo, Romeo’s rival for Giulietta/Juliet’s love and her father’s preferred suitor. Portillo stood up to the music stand and offered singing notable for its ease and fluency, and for its ability to be not only ringing but gentle and soft when called for, pulling back to a kind of white limpid sound that’s not often heard these days . It was just plain pretty

But for sheer beauty of sound, it would be hard to top Lindsey’s first notes. Lindsey cultivated a rich, deep voice that turned out to sheathe a higher-placed and brighter sound once she got going in this often hell-for-leather score. However it varied through the evening, she never lost her smooth vocal line and, even more significantly, her utter investment in the role. Opera singers often seem to me to offer diction, coupled with gesture; Lindsey offered words linked to a character, without forcing anyone to decide whether music or acting came first. In short, she’s the real thing.

The star of the show was supposed to be Olga Peretyatko, who shone in the Metropolitan Opera’s “Puritani” this spring, but illness forced her to withdraw in favor of Nicole Cabell, who sang Medora in “Il Corsaro” here in March, and who made her San Francisco Opera debut as Giulietta in this opera two years ago. Cabell’s honeyed soprano proved better suited to Bellini’s rich melodies than to even middle-period Verdi, and she and Lindsey were well scaled to each other, although she sometimes seemed a touch mannered in comparison. As her father, Capellio, Jeffrey Beruan showed a promising, weighty bass voice.

Because the romantic leads are both taken by female voices, the biggest duet for tenor and high voice is a standoff between Tebaldo and Romeo. Oddly, Portillo and Lindsey were less effective here — slightly muffled, perhaps, by the orchestra. Antony Walker, WCO’s energetic conductor, seemed to have trouble bringing them into line; the opening was blurred and muddy, and there was a lot of sloppy playing, in contrast to his crisp podium manner. The chorus enjoyed itself, though, and the audience certainly did.

The Washington Concert Opera’s next production will be “Guntram,” Richard Strauss’s rarely performed first opera, on March 1. For more information, visit www.concertopera.org.