There’s a whole lot of loving going on at the National Symphony Orchestra this weekend.

Its current program, which opened Thursday, focuses exclusively on pieces about tragic romance, expressed fulsomely, from Wagner’s Prelude and “Liebestod,” from “Tristan und Isolde,” to Tchaikovsky’s “Romeo and Juliet” and — possibly gilding the lily — “Francesca da Rimini.”

In between those two composers comes the most aching and poignant work of all, Peter Lieberson’s “Neruda Songs.”

Let’s not get hung up on whether I just implied Lieberson was greater than Wagner. Let’s not, in fact, get hung up on anything I have to say about the “Neruda Songs.” They’re a stunning cycle, a sincere gesture of love, written by a husband to and for his wife, and simply beautiful music. You should go and hear them for yourself.

Forget about last week’s gala: Thursday night marked the real opening of the subscription season, and having “Neruda Songs” on the program, a solid artistic experience, made it an auspicious beginning. True, the program as a whole was florid, to say the least — it was a lot of big, passionate love and loss for a single evening. But this is right up conductor Christoph Eschenbach’s alley. Whatever unclearnesses I may find in his beat or quibbles with his balances, he knows how to churn an orchestra into passion. The big, swelling climaxes, both of the “Liebestod” and of the “Romeo and Juliet,” certainly hit the mark.

And the orchestra is undeniably sounding better. It’s more robust, more energized, with signal improvements in the brass, as you could hear in the Wagner, and winds, as you could hear, particularly, in “Francesca da Rimini,” which might have seemed superfluous on a generously long program but justified its place by showcasing some of the principal wind players to advantage.

All the Romantic framing was probably a way to keep audiences from being scared off by the contemporary piece. If only they knew that the five “Neruda Songs” were the highlight of the program. The solo part was written for the radiant mezzo Lorraine Hunt Lieberson, who died only a year after she sang the premiere, and it is almost impossible to read the words without tearing up (“My love, if I die and you don’t — / My love, if you die and I don’t — let’s not give grief an even greater field”).

That was probably not the reason the Kennedy Center Concert Hall was kept too dark to read the printed program comfortably, but I would wager that a good portion of the audience didn’t actually know what the singer was saying.

That singer was Kelley O’Connor, who worked with the composer on the piece after Hunt Lieberson’s death and before the composer’s own, in 2011. O’Connor certainly knew what the words meant and delivered them in a beautiful, rich, dark ribbon of sound. You could argue that there might have been more freedom in the voice — that she kept it dark and contained and put a little extra strain on her singing — but it was a stellar performance that manages to express love in beautiful music that’s neither sappy nor retro.

Happiness and love, in Lieberson’s setting, are things too grave and tremendous to be merely pretty or merely ecstatic. There’s a dark undercurrent, like a foreshadowing of tragedy to come, that makes the gleam of its gladness (“And now you’re mine. Rest with your dream in my dream”) shine like dark gold through the articulate music all around it.