There are all kinds of musical love notes, but surely one of the most devastatingly beautiful manifestations of the form in this still-young century is a set of songs by Peter Lieberson.

Conductor Stéphane Denève called the Neruda Songs a “masterwork” Thursday night before leading the Philadelphia Orchestra in its first-ever outing with the piece, with mezzo-soprano Kelley O’Connor.

Denève is correct. The songs are wonderful, and their status as a singularly personal statement seems to have grown only more intense since their arrival a decade and a half ago.

The ink was still wet when they were first heard in Verizon Hall in 2006, performed by the source of their inspiration, the composer’s wife, mezzo-soprano Lorraine Hunt Lieberson, with the Boston Symphony Orchestra. She died a few months later, at age 52.

O’Connor has performed the Neruda Songs often, and taking up the piece as she has is an act of rescue from the trap of works too closely identified with their progenitors. As captivating as the back story is — “one of the most extraordinarily affecting artistic gifts ever created by one lover to another,” Tim Page wrote in the Washington Post — there is an inherent inner glow that makes these songs worth hearing over and over.

In 30 minutes, they create a world apart. The texts are from poems Pablo Neruda wrote for his wife (an additional layer of personal intensity), and as the songs intermingle images of love and nature, Lieberson draws suddenly shifting moods and varied glints of color from the orchestra.

And what moods. There’s a sensation of floating in the second song, which evokes clouds and heavenly blues. Quiet, pensive beating threads through the third song, which speaks of fear of being left behind, alone, an anxiety O’Connor heightened by pushing her low-rich voice to the edge of vulnerability. “Will you leave me here, dying?” the last line asks, followed by tender strings fading to nothing.

The strongest influences in these songs might be Debussy and Berg. But it’s hard not to think of Strauss in the gauzy light of the last one. The title translates as “My love, if I die and you don’t.”

Like Strauss, the scoring brings forth a lot of solo voices from the orchestra. Some are fleeting, like the stylish stroke by horn player Jeffrey Lang at the end of the first movement.

The showcasing of solo voices continued into a performance of Stravinsky’s The Firebird. One after another, the orchestra’s wind players unfurled impressive solo work. Particularly notable: Erica Peel’s lovely laser of piccolo sound, flutist Jeffrey Khaner’s silken passages, and hornist Jennifer Montone’s expressiveness.

Here, Denève led the complete ballet music rather than the more commonly played suite, and the longer version more than justifies itself. For one thing, it’s all gorgeous. For another, it’s only in the full score that you’re able to make connections between The Firebird and other Stravinsky works. Plus, the connective tissue lost in the suite makes you hear the suite’s music you thought you knew in a new light.

An exotic voice was introduced into the ensemble for Lera Auerbach’s Icarus for Orchestra. Most of us know it as the sound of monster movies, but here the theremin, played by Darryl Kubian, was divorced from its more kitsch context to become a sly element in the orchestral color.

High-energy, then lurching, then gentle and luminous, the short piece made one visualize the journey of our hero. But it turns out that Auerbach’s title came after the music was written. Hewing to the literal in music isn’t as dangerous as flying too close to the sun, unless you consider a lack of imagination to be a fatal flaw. Auerbach not only survived the flight unscathed. She soared.

Additional performance at 8 p.m. Saturday, Verizon Hall, Broad and Spruce Streets. Tickets are $10-$164. philorch.org, 215-893-1999.