Sung in a mild voice, Cass McCombs’s songs in “Mangy Love” are tightly packed with defiance, nihilism and esoteric jokes (Rachel Pony Cassells)

I once asked Cass McCombs a question about the significance of spontaneity in his songwriting. He ended up explaining why all music is fundamentally sad: As sentient beings, we’re always departing an irretrievable present, which leaves us in a perpetual “state of melancholy” — a sorrow that infuses all knowledge. “The only time you know anything is looking back,” he said. And just like that, I’d been convinced that the present moment has never existed: We’re always living in some form of the past. Outside the bar where we’d met, snowflakes were falling, melting on contact with the pavement like tiny metaphors.

It’s possible that I misunderstood his point completely, but either way, I’ve thought about this conversation nearly every day of the 32 months since it took place. If our temporal existence is a continued exercise in mourning, the laws of physics seem to back it up. To look at something just one foot away from your face is to peer into the past, one billionth of a second back in time. Sound travels even slower than light, of course, which means that songs actually memorialize themselves as they unfold.

That’s one of the terrific riddles embedded in McCombs’s music. Another is how it generates such heavy thoughts while feeling almost ridiculously light. The 12 songs on “Mangy Love,” the singer’s impeccable new album, float off the speakers like plumes of rainbow smoke, delicate and beautiful, then gone. They often resemble folk songs from the 1970s, sometimes set to reggae rhythms, sometimes decorated with little R&B guitar flourishes. It’s a slightly louche sound, but not in a way that makes you feel queasy.

These songs would lose nearly all of their magnetism without McCombs’s lyrics, which are some of the greatest you could hope to hear nowadays. Sung in a mild voice, they’re tightly packed with defiance, nihilism and esoteric jokes — all of which create a bizarre, exquisite friction against the calm of the music. Plus, it’s always a kick to place your trust in a narrator who never seems to want it.

Serenity and disaster await on the album’s opening cut, “Bum Bum Bum,” a gentle song with a titular refrain that McCombs sings like it’s la la la, even though the neighboring lyrics conjure the dun-dun-DUN of a black-and-white horror movie. “No, it ain’t no dream, it’s all too real,” he exhorts with lullabye softness. “How long until this river of blood congeals?”

Like anyone who’s gifted with words, McCombs also knows how to hurl an insult. He asks some poor character, “What Fresno tweaker’s ashtray you crawl from under?” That’s a line from “Rancid Girl,” a relatively boisterous, electric-blues number that could very well be about a girl who digs the ’90s punk band Rancid. And when other scraps of pop-junk wash up in these ballads, he likes to give them a twist. During the Friday night strut of “Cry,” he converts three words of millennial sex slang (“Netflix and chill”) into an option for doomed lovers (“Netflix and die”). During the breezy existentialism of “Opposite House,” he seems to be grabbing onto the logic of an ancient Paula Abdul lyric: “One step forward, two steps back/They say opposites attract.”

This stuff might sound cute on paper, but in open air, in real time, it’s strangely devastating. Maybe this music is all about grieving the passage of time. If so, McCombs appears to be pushing back on the rules of temporality during “Medusa’s Outhouse,” where he slips into his sweetest don’t-wake-the-neighbors falsetto and pleads, “Help me to remember to forget/To forget what hasn’t happened yet/Knock me down that mystic slide again.” Watch him go.