Golden lions and floral embellishments parade across a lapis-blue ground, while women in white robes lounge in honey-colored light. This could be a description of a painting by Delacroix or Gerome, masters of 19th-century Orientalism. But it also describes the hand-painted set flats and costumes of Verdi’s “Nabucco” in its new production at the Washington National Opera, which opened Saturday night.

The idea was to show how this opera, Verdi’s first major success, might have come across to an audience at its 1842 premiere at La Scala. To underline the point, Thaddeus Strassberger, the show’s director and set designer, presents it as a play-within-a-play, enacted before a 19th-century audience with a row of armed Austrian soldiers making sure things don’t get out of hand. The play-within-a-play idea has been done to death, but I was tolerant because I got such a kick out of Strassberger’s evocation of opera of a bygone age, and without the frame, the old conventions he duplicated might have come across as wooden.

From this production, one could surmise that Strassberger is a better set designer than a director. The sets were pretty wonderful, and the basic ideas were reasonable — I liked, for instance, the idea that the whole end of the opera, with its surprisingly pat resolution, is a fever-dream of the imprisoned Nabucco, who summons up the spectres of his past in a rosy daydream haze before falling dead. But the execution was a little clumsy, and not only because Strassberger was drawing on bygone conventions.

Spoiler alert: If you want surprises, read no further. Strassberger’s concept centered on the famous chorus “Va, pensiero,” sung in the opera by the Hebrew slaves, which in 19th-century Italy became a veritable anthem of Italian independence. For it, Strassberger moved the audience behind the scenes, so that we saw ballerinas practicing, stagehands moving sets, seamstresses sewing costumes, while the chorus sang in the background. But the scene failed to convey the kind of electricity that was called for. In fact, after the gorgeous opulence of the preceding scenes, it fell a little flat, and the traditional encore seemed dutiful (though it allowed the orchestra to play it without the obvious slips that marred it the first time through) — especially because the audience, at the work’s first WNO performance, didn’t know it well enough to follow tradition and sing along. The evening never quite recovered its energy.

There was still a lot to enjoy. I’m a sucker for Verdi, and while it becomes ever more evident that true Verdi singers are a rare breed these days, WNO assembled a cast — most of the singers in company debuts — that could at least hit the notes and make the thing go. The historicity of the sets helped create the illusion that we were hearing the singers at the premiere, who (obviously) didn’t quite know how Verdi singing went either.

All that was missing was the superstar quality — the sensuality of reveling in sheer vocal sound — that probably characterized the two soloists for whom Verdi wrote the leading roles of Nabucco, the king of Assyria and rebuilder of Babylon, and Zaccaria, the high priest of the Israelites. But if Burak Bilgili (the Zaccaria) didn’t quite have the ideal thundering presence, and if Franco Vassallo’s Nabucco sounded a little constrained at times, both delivered honorably.

Similarly, the soprano who first sang the killer role of Abigaille — Giuseppina Strepponi, who a few years later became Verdi’s lover and, ultimately, his wife — must have had a strong lower register, or Verdi wouldn’t have called on her to use it so much; Csilla Boross, a soprano from Hungary, didn’t. Abigaille is the pivotal, villainess role: She starts out thinking she’s Nabucco’s daughter, learns she’s the child of slaves and, nonetheless, seeks to take over as ruler after God strikes the blasphemous Nabucco mad. Boross’s concept involved hurling out big, loud, brassy top notes, which were fine, but her passage work was approximate and her low notes almost inaudible. As Fenena, Nabucco’s actual daughter who converts to Judaism partly for love of the handsome Ismaele, the mezzo-soprano Geraldine Chauvet had a much more consistent, even sound, effectively showing how it can be done.

Sean Panikkar was an Ismaele who made up in presence and ardor for what he may have lacked in vocal heft; he continues to be someone to watch. And a couple of the young artists from the Domingo-Cafritz program acquitted themselves very well: Soloman Howard seemed to be channelling the Grand Inquistor from Verdi’s much later “Don Carlo” as a doddering High Priest of Baal with a strong bass voice, and Maria Eugenia Antunez was striking in the often invisible role of Anna. Jeffrey Gwaltney is a towering presence as the all-purpose warrior figure Abdallo, but he took a while to warm up.

But the main musical force were the WNO chorus and orchestra under Philippe Auguin. What the orchestra did may not have exactly been idiomatic Verdi playing — it was a little too careful and obedient — and Auguin’s tempi sometimes dragged, but it was generally clean and lively. And the chorus, which has a major if not the main role in this opera, rose to the challenge with a kind of energy and power. It was a delight to hear from the chorus.

What was the actual premiere of “Nabucco” like? I imagine it all a little more down and dirty, with big personalities and a verve that made the audience actually want to sing along. Culturally, we may be too far removed from that time to actually re-create it.

Another spoiler alert: When the curtain calls came, Boross/Abigaille suddenly shushed the audience and began “Va, pensiero” again, while the supertitles flashed the Italian words to enable the audience to join the assembled cast in an a cappella rendering that was some of the evening’s most honest and moving singing yet. But the opening-night audience sat silent. One hopes that future audiences will warm to Strassberger’s karaoke-opera attempt and join in.

“Nabucco” continues through May 21 at the Washington National Opera.