I’m listening to the latest Stephen Spencer song when suddenly I burst into tears. Was it the falsetto vocals? The swirling harmonies? No, it was the lyrics: “What did Apple-the-Stoola say? He said ‘I love you’ twenty-sixty times.”

Spencer, you see, has a unique lyrical collaborator: his three-year-old daughter. Over the last four months, he has been posting short songs online based on her stream-of-consciousness stories. There’s a smooth soul number about “a regular rabbit, who has regular ponytails just like me”. A song called Funchy the Snow-woman that could fit easily on to a 1975 album, but for its lyrical message about using a litter tray in the forest. And a festive tune about a Christmas cat called Harda Tarda, who hopes that Taja (“a funny way to say Santa”) will bring her “a doggy, a puppy and a ninja-bread man”.

When he started posting his songs, Spencer had 36 followers. “They were really just for my mom and her book club.” He now has more than 250,000 and his songs have been listened to an astonishing 23m times on Instagram and 5m times on TikTok. There have been demands to turn these minute-long mini-masterpieces into full-length versions for an album. “I’m hesitant to try to stretch them in a way that might spoil the magic of those captured moments,” he says. But there are plans to release something in longer form. A Spotify release of Regular Rabbit is set for this week.

On first listen, the songs are funny and cute, a welcome respite from the tumult in the world. But they’re also absolute bangers. Spencer – who was in a funk band at school in Ottawa and is now professor of composition and music theory at Hunter College in New York City – is incredibly adept at crafting hooks that won’t leave your head. But what about the crying? Because I really did not expect that.

“I think the songs resonate with parents of children who are no longer three,” says Spencer, by video call. “There’s something fleeting about those first few years. I’ve always had a sense of wanting to bottle it because I know it will disappear soon. Music is my way of doing that.”

This makes sense. My daughter is nine now and, although she still writes charming stories, the surreal character names and dream-logic plotlines have been replaced by more sensible tropes. Hearing Spencer’s songs takes me straight back to that giddy toddler period.

But is it more than nostalgia? Spencer, 35, has noticed another surprising response to his work. He’s aware of the inherent humour in the contrast between his daughter’s flights of fancy and his meticulous approach to performing them seriously: the way he turns to the camera to sing passionately about, say, a dinosaur called Pasghetti is reminiscent of Flight of the Conchords. “But what I didn’t realise,” he says, “is how that would land, for so many people, as an act of love. Listening really closely to a child, taking care in understanding, trying to get the words right, no judgment, no correcting – that turned out to be really moving for some people.”

Indeed, fans love the fact that characters in the songs goed somewhere rather than went, or flied instead of flew. “Some people have said that the songs touch them because they were never deeply listened to as a child,” says Spencer.

The comments under his songs on Instagram (@_stephenspencer) can be as moving as the music. Under the one about Apple-the-Stoola (an apple man who is granted wings by a fairy so he can fly away and find his lost mum), a listener has posted: “I wish I could still tell my Mom I love you twenty-sixty times. She ‘flied away’ nine years ago. So if you still have a mom that is in your life, tell her ‘I love you’ twenty-sixty times.”

“There’s this tendency to interpret her words in a profound way,” says Spencer, who chooses not to give his daughter’s name. This is not entirely accidental. Spencer picks out phrases from the stories he thinks have the potential for deeper meaning and uses them for chorus refrains. In the Christmas cat song, Santa responds to present requests by saying: “I’ll give you everything.” Watching Spencer sing this, from the heart with his eyes closed, it’s clear that, although these are his daughter’s words, he’s really saying them back to her.

It’s not his only clever musical trick. While listeners like to compare his work to yacht rock and other breezy 1970s genres, Spencer says his influences are jazz and classical. “In my theory classes, we often look at Beethoven. There might be a chord change in the development of a sonata where he will modulate to a foreign key. I try to use that same technique for my pre-choruses and bridges.”

Has the growing audience added pressure and expectation to something that started out extremely pure? “I have to forget about that side, because what makes them work is how it’s about just hanging with my daughter and not taking life too seriously.”

The songs normally come together over a couple of afternoons. Spencer will record her stories on his phone and, occasionally, go back for more details if he feels the verses need an extra syllable here or there. It’s a genuine artistic collaboration. So what does his lyricist make of the results? “It’s maybe a little disappointing as an answer,” he says, laughing, “but from what I can tell, she couldn’t care less. Let’s just say she’s more focused on the process than the product.”

A true artist then! “Exactly. I’ve told her 20 million people have listened, but that’s not really a meaningful number to her. Put it like this: she thinks I’m seven.”

• Regular Rabbit (Living Room Version) is released on streaming platforms on 17 February