Ms. Goerke sang splendidly, with silvery top notes and earthy colorings lower in her range . Still, she seemed to be feeling her way into the role — at least the 80-minute chunk that is Act II, most of which is devoted to an impassioned love duet. When Isolde, in a wild-eyed moment, tells her nurse that the goddess of love commands her to plunge into the realm of night, Ms. Goerke’s singing had sheen but lacked blaze.

There was something affecting, though, about this slight feeling of tentativeness in her performance. Here was a great singer making herself vulnerable and inviting an audience to share as she took up one of opera’s great challenges.

In music that’s often conducted with thick, rich sound, Mr. Noseda drew lucid, fleet and textured playing from the orchestra during urgent stretches of the score. The opening of this second of three acts — when a nervous Isolde is waiting for Tristan to arrive as horn calls from a nighttime hunting party are heard in the distance — was wonderfully restless and lithe. As the act progressed, Mr. Noseda was good at revealing the shape of long arcs in the score, as the music swelled and crested and subsided.

At times, for all the bracing vigor and transparency, I wanted more traditional Wagnerian weightiness and depth. Mr. Noseda was at his best as the music settled into the murmuring, blissful “O sink hernieder” love music, which had hints of almost Italianate lyricism in this performance. Ms. Goerke and the tenor Stephen Gould exchanged long-spun, melting phrases while the orchestra shimmered; subtle syncopations in the warm strings came across like nervous breathing.

Mr. Gould was not testing any waters: He has long been a leading Tristan. At times his voice sounded a little patchy and rough. But he mostly sang with remarkable freshness and clarion tone, especially during Tristan’s bursts of unhinged ardor, and brought touching poignancy to moments when he was transfixed by Isolde’s rapturous love.