Antony Walker, far right, conducts Marjorie Owens (Leonore), left, Celena Shafer (Marzelline) and Eric Halfvarson (Rocco) in “Leonore” at the Washington Concert Opera. (Don Lassell)

Beethoven wrote only one opera, but he wrote it a couple of times. The first version, known as “Leonore,” was a flop. Admittedly, this was partly because the French had recently invaded Vienna at the time of the premiere, so the sparse opening-night crowd was made up largely of French officers, giving some spice to an opera about heroism in the face of unjust tyranny.

Beethoven then spent 10 years struggling with the piece before presenting “Fidelio,” the version the world now knows, in 1814. “Fidelio” remains an awkward opera, though it contains some of the most powerful music in the canon. On Sunday night, the Washington Concert Opera presented “Leonore,” the original version, which turned out to be a veritable missing link in understanding how “Fidelio” got to be what it was — as well as a vocal cornucopia.

“Fidelio” and “Leonore” — the stories are the same — are about a woman who disguises herself as a man to gain access to the prison where her husband has been unjustly jailed. Both, too, begin as domestic comedies and end up as heroic dramas. A big difference is that the earlier “Leonore,” in three acts rather than two, describes a gentler progression from one extreme to the other, where “Fidelio” lurches between them abruptly, but with greater musical force. Hearing “Leonore” is like taking a trip inside Beethoven’s head as one learns what was lost along the way: a lot of mitigating, gentler and undeniably beautiful music, including a duet for Leonore (the disguised wife) and Marzelline (the jailer’s daughter who has a big crush on the young man Leonore is pretending to be). There also are four versions of the overture; Antony Walker, WCO’s music director, led the first (known as “Leonore 2”), a far gentler and more narrative journey through the piece than the heroic blasts that open “Fidelio.”

Celena Shafer, as Marzelline, oversold her opening aria, but settled down in subsequent ensembles. (Don Lassell)

You could argue that Beethoven’s earlier opera calls for lighter voices than the powerhouse that “Fidelio” eventually became, but WCO chose to cast it with full-on dramatic singers, led by Marjorie Owens as a radiant-sounding Leonore, despite an oddly low-key stage presence. The gentler vocal writing showed an unsuspected sweeter side to the sound of Simon O’Neill as the husband, Florestan. Pizarro, the villain, is still called upon to thunder and fulminate; I confess that after Washington National Opera’s “Ring” last year I so identify Alan Held with Wotan that it was odd to hear him incorporate such a bad guy — Pizarro is an unhinged leader who locks up his political enemies at will — with such conviction and force. 

The domestic-comedy side of the piece isn’t actually all that funny, since the jailer, Rocco, is the archetype of the small official who loves his family but slavishly follows unjust orders. Eric Halfvarson, though, manages to make everyone he sings slightly lovable, and he sang his way past an announced and initially audible indisposition into a warm, blunt, honest sound that effectively let the character off the hook. His daughter, Marzelline, was sung by Celena Shafer, who oversold her opening aria with too much extra cuteness, but settled down in subsequent ensembles and showed that she still commands the fulsome beauty of tone many of us remember from the start of her career.

The WCO orchestra’s thin sound definitely represented a lighter approach to this big score. As for the chorus, it was brought into the spotlight, coming out onto the front of the stage for such key moments as the prisoners’ chorus and the extended finale. Gazing rigidly out at the chorus master, Bruce Stasyna, who conducted from the audience, and nervously consulting pieces of paper with their parts, they gave a convincing portrayal of people being awakened from long, unquestioning passivity, while Walker ardently gestured behind and around them, out of their line of vision, as if trying to wake them up.