The Grownup Noise singer-songwriter-guitarist Paul Hansen co-wrote new song “Plaything” with an unlikely collaborator. The song’s lyrics come from a poem his great grandmother penned more than a century ago.

“I’m like the black sheep of all black sheep in my family, a family where everyone is doing very normal and noble stuff and would ask, ‘Why are you studying music?’ ” Hansen told the Boston Herald. “Then I discovered my great grandmother was creative, a poet, a songwriter, a painter.”

A few years ago, the family uncovered some treasures from the life of Blanch Marie, Hansen’s great grandmother. Sifting through journals, rejection letters from song publishers (one of which Hansen framed), and more, he found the 1917 poem “Plaything” and began to adapt it into a song.

“When I started to write the song, I tried to write it in the style of the 1910s and it just sounded really corny,” Hansen said. “Then I tried the poem with a chord progression that I had been messing around with and I went, ‘Whoa, this works as a modern song,’ and it blew me away.”

“Plaything” is classic the Grownup Noise: extremely catchy indie pop spiked with dark melodic turns fueled by a tender cello line and a gentle break with cooing harmonies. The song is sophisticated and simple, sad and somehow triumphant.

The surge of inspiration kicked off a burst of writing that came at the perfect time for the Boston band. After making 2020 Grownup Noise’s “Lonely Days” as essentially a solo record, Hansen found his original bandmates ready to reunite — cello player Katie Franich recently moved back to town, after getting burnt out, bassist Adam Sankowski felt ready to jumpstart the old line up, and even ace session and touring drummer Kyle Crane found time in his schedule to make new music.

Weekly meetings with Hansen, Franich, and Sankowski turned into a dozen fresh songs with deeply collaborative arrangements. Those became the new LP “No Straight Line in the Universe” — which gets a Feb. 7 release party at Medford’s Deep Cuts.

“We’re old now,” Hansen said — “No Straight Line in the Universe” comes nearly two decades after the band’s debut. “And boring. But we have a lot to say now to each other and you can hear that in the music.”

“No Straight Line in the Universe” is full of adult themes delivered with youthful energy. The delicate “We Become Roses” deals with how hard it is to help struggling friends when adulthood’s realities keep people apart. “Anxiety” may be the most hypnotic tune written about dread (it’s those intertwined Hansen and Franich vocals over an organic Stereolab vibe). A few more uptempo tunes look back on what could have been with a mix of nostalgia and a, well, grownup perspective.

Of course adult themes aren’t boring. In fact, more rock acts need to have the honesty to address them. And despite the cello, heavenly harmonies, and intricate songcraft, the Grownup Noise is a rock band — and the emphasis should be on the world “band.”

Because Crane is such an in-demand drummer, he can’t devote a ton of time to the band so old bandmates and friends will be called on for upcoming shows. But the core of Hansen, Franich and Adam Sankowski have ambitions beyond the new record.

“Once I get new songs it’s fun to have a place to put them,” Hansen said. “We’re all dug in here so there won’t be a large gap between albums (like over the past decade).”

For the Grownup Noise, the past — from a great grandmother to recalling what pulled the members together two decades ago — is fueling the future.

For details and tickets, visit thegrownupnoise.com