Emiliano Gonzaelz Toro as Nourredin in rehearsal for “Lalla Roukh.” (Louis Forget)

No one in the Eisenhower Theater on Saturday night had ever seen the opera that was being presented. For audiences of Opera Lafayette, that is hardly unusual. The Washington-based company specializes in French baroque opera, and has made a international name by exhuming neglected works on stage and CD: Rebel’s “Zélindor” and Philidor’s “Sancho Pança.”

But the opera the company mounted Saturday under the company’s founder and music director, Ryan Brown, was of far more recent vintage: Felicien David’s “Lalla Roukh” opened at Paris’s Opera-Comique in 1862. This isn’t baroque opera; this is a 19th-century proto-musical, complete with exotic locale, pretty tunes, spoken dialogue and a sweet, happy ending. Some works have been neglected because they push the envelope or are ahead of their time; “Lalla Roukh,” which before Saturday hadn’t been performed for more than 100 years, has been neglected perhaps because it was so very much of it.

Although not earth-shattering, “Lalla Roukh” is certainly as good as plenty of other shows that have managed to keep being performed. It’s the story of an Indian princess who has been pledged in marriage to the king of Samarkand, but who, on her way to meet her betrothed, falls in love with an itinerant minstrel. She defies the king and pronounces her love to the world — only to find that the minstrel is actually the king himself. This straw-man plot is an excuse for lots of perfectly beguiling tunes and love duets and a broad comic role for the scheming buffoon of an official, Baksir, who has been entrusted with bringing Lalla to the king.

Opera Lafayette has been nosing around the roots of the opera-comique genre for some time, from Philidor to Monsigny (whose “Le roi et le fermier” it performed last February at Versailles), so “Lalla Roukh” isn’t a complete departure. The production, however, did represent a considerable step up the evolutionary scale. This company used to specialize in concert readings with an occasional bit of stage business or danced interpolation. “Lalla Roukh” was almost completely staged, however, directed by Bernard Deletré, with full costumes by the New Delhi-based designer Poonam Bhagat for everyone but the chorus (which sang mainly from the back of the stage, behind a scrim).

The other main feature of the performance, which was partly supported by the Indian ambassador, was the company Kalanidhi Dance, presenting the dance elements in traditional Kuchipudi style and adding a danced prologue to set the scene. It was a slightly uncertain marriage: The dancers were wonderfully interpolated into the main action, but the recorded music of the prologue made a jarring contrast with the live score — and to judge by the applause, the dancers were the main attraction for at least a vocal portion of the audience.

Bernard Deletre as Baskir in rehearsal for “Lalla Roukh.” (Louis Forget)

Venturing into fully staged opera brings Opera Lafayette onto a new and larger playing field. On Saturday, however, it was not the staging but the musical side that seemed slightly uncertain. Not surprisingly, Brown and the orchestra members — who are used to playing baroque works together and without a lot of rehearsal time — did not sound fully at home in this 19th-century idiom; awkwardnesses of phrasing and balance stood out, though they might improve, now that everyone has one performance under their belt. (The production travels to Lincoln Center next week for one performance.)

There was also notable unevenness among the international cast. Marianne Fiset, making her company and Kennedy Center debuts in the title role, had a tendency, in the first part of the show, to go flat — though she had a pretty voice and did much better when she had warmed up.

As the king/minstrel, a.k.a. Noureddin, tenor Emiliano Gonzales Toro had a nice, light weight and color but absolutely no body behind his upper notes, which simply didn’t sound out. Deletré himself took the role of Baksir and tried to make the role broadly funny without overplaying it too much, offering the requisite comic shtick as he pursued Lalla’s servant, Mirza, sung capably by Nathalie Paulin.

It was all adequate without being quite impressive — musically, that is. The most impressive thing is the growth of Opera Lafayette. Yet again, it gave people a chance to hear a work that is occasionally cited, but never performed — and to ponder the question of why some innocuous and pretty works are remembered while others are forgotten.