Last week, I wrote two stories about the Washington National Opera’s “Tristan und Isolde,” which opened Sunday afternoon at the Kennedy Center. One of the stories was about the eleventh-hour replacement of the soprano originally scheduled to sing Isolde, Deborah Voigt, whose face still graces this month’s Kennedy Center playbill. The other was about the opera itself and touched on the way that the orchestra does the heavy lifting, bearing the voices along on an inexorable tide of sound.

You’d think that this juxtaposition would have better prepared me for what happened on Sunday: a performance by Philippe Auguin, the WNO’s music director, and the WNO orchestra that was so compelling that the singing seemed only of secondary importance. Put more candidly: The fact that the singing didn’t captivate me across the board did not prevent me from being deeply caught up in the performance.

Voigt’s cancellation was probably best for all concerned. Voigt, 53, is not fully a Wagnerian in the sense that her 50-year-old replacement, Irene Theorin, is. Ideally, you want a stunning sound from an Isolde, but at the very least you don’t want to have to worry about the singer; Theorin has sung the role around the world and has a big honker of a voice.

Indeed, after hearing her only a few times (most recently in the WNO’s “Ariadne auf Naxos”), I had an impression that she was simply a loud singer, and was therefore happily surprised by the nuanced, quiet singing that proved to be the best feature of Sunday’s “Isolde.” In a lot of Act I, and quite a bit of the concluding “Liebestod,” what captured your ear was not a huge sound but focused singing over a hushed orchestra that brought out the chamber-opera elements in this powerhouse role. Little of the color and nuance of these moments survived when she opened up her fortes in long-standing, pumping-out-sound Wagnerian tradition, but they added a lot to her portrayal.

Tristan is a thankless role. Both these lead roles are legendarily difficult, but the tenor has to hold the stage alone for a punishing marathon at the start of Act III, after which Isolde steals the show with the “Liebestod,” one of the greatest moments in all of opera. (Forgive the hyperbole, but it is, for once, warranted.)

If these observations qualify my criticisms of the tenor Ian Storey, so much the better; sadly, I didn’t find much to be thankful for in his portrayal, either. He is capable of making some beautiful sounds when he pulls the pressure off his voice — his crestfallen reply to King Marke (Wilhelm Schwinghammer), after Marke’s anguished monologue about the betrayal of finding Tristan, his best friend, sleeping with Isolde, his wife, rang true as crystal. But in many of the heightened moments with Isolde, Storey’s voice took on the unclear quality of conglomerate rock, a sense of a slightly grainy composite.

Both Tristan and Isolde have sidekicks: part of Wagner’s compositional balance. Both of them took a while to warm up on Sunday: part of the breaks of opening day. Elizabeth Bishop, as Brangäne (she who swaps out Isolde’s death potion for a love potion in Act I) fell a little flat during her gorgeous supporting role in the Act II love duet but regained crispness, clarity and color in Act III, while James Rutherford, as Kurwenal, Tristan’s loyal henchman, somewhat improved on a sound that had been wobbly and off-pitch.

Both Rutherford and Schwinghammer were making company debuts; Schwinghammer offered an honorable performance of Marke, opera’s ill-starred cuckold. The Domingo-Cafritz program distinguished itself: Norman Garrett had a nice moment as the Steersman, Yuri Gorodetski sounded appropriately youthful and clarion as the young sailor at the beginning and the shepherd at the end (more balance), and Javier Arrey, an alumnus of the program, was impressive in the small villain’s role, Melot.

It’s customary, in a review of a new production, to talk first about the production, but it may be a virtue of Neil Armfield’s that it offered so little to discuss. It was first seen at Opera Australia, and the company itself is credited with the set design, a single flat raked plane suspended from fine wires over a thin sheet of water: boat-like in the first act, representing the tenuous nature of reality, or the lovers’ tenuous hold on it, in the next two. The costumes, by Jennie Tate, were standard-issue medieval-period: voluminous white robes for Isolde, leathery tunics and capes for the men.

None of this got in the way of the action, and Armfield, happily, focused not on concept but on character, finding the humanity in figures that can sometimes seem like onstage archetypes: for example, bringing out Isolde’s girlish impatience at the start of Act II. The only real distraction was the decision to stage the prologue; the playing of the orchestra was so powerful, from the opening bars, that I would have preferred not to have the visual distraction.

Auguin has said before that he wanted to show, in Washington, that he isn’t just a Wagnerian, leading everything from “Madama Butterfly” to “Manon Lescaut,” but with this performance he confirmed for me that Wagner sits solidly in his wheelhouse as some of the other repertoire does not.

The playing was moving, nuanced and gentle, not always an adjective that you think of with Wagner. If there were chamber elements in this performance, it was because of the way that Auguin led rather than drove, giving plenty of room for wind solos, for example, to stand out. My biggest quibble was the supposedly climactic love duet, which was simply too fast — but as Auguin said in a phone interview with me before the performance, you have to compromise some of the tempi in Act II if you want the singers to be able to get through Act III. There were plenty of other pleasures to make up for it.