At once jaunty and dark, the music of the Canadian singer-songwriter has won him a growing fanbase. On his third album he addresses his ‘old man’, an alcoholic and addict he barely knows

Early March, north London. Three hundred youthful-looking people have wangled tickets to see Canadian singer-songwriter Mac DeMarco perform a rare intimate gig at a tiny pub called Nambucca. For the rest of the year he’s on a massive tour of the US and Europe – including two sold-out nights at south London’s 5,000-capacity Brixton Academy and headlining End of the Road – but tonight he’s performing solo, no backing band, “just Mac”.

Beloved by critics and with a devoted fanbase – his last album, Salad Days, sold more than 100,000 copies in the United States – DeMarco has built a career on his mellow tunes and amiably scruffy, gregarious persona; qualities that are on full display tonight. He jokes around with the audience, delivers note-perfect renditions of new material and old favourites (with the crowd filling in for the guitar solos where necessary), his stage banter is charming and good-natured. He takes increasingly frequent swigs from a bottle of tequila: “This is the most drunk I’ve been on stage in a long time,” he declaims to loud cheers two-thirds of the way through. The last song culminates in a 10-minute stage dive.

It’s always weird when someone takes their pants down and has a drawing of me tattooed on their butt. That’s happened

When I speak to him on the phone from his home in LA nearly two months later, he has just come from two weekends at Coachella, where he was described by the Guardian as possibly “the perfect late afternoon festival act”. His third studio album, This Old Dog, has been leaked online, but he is – naturally – chill about it, telling fans to download it from “Pirate Bay, Torrents.to, Soulseek, Napster, Limewire, Kazaa. Just get it.” The album in question is a more sombre, thoughtful affair than his previous work: although there has always been a bittersweet melancholy to his songs, questions of ageing and growing up (in a few days DeMarco will turn 27) permeate the lyrics here.

But it’s Monday morning, he’s just woken up, and he’s in no mood to enter that headspace. When I remark that the album has more darkness and meditations on mortality, he yawns and says, “Maybe, I dunno. Maybe I was just being a jackass.” Has he picked up any adult life skills recently? “Uh I don’t think I have very many… fuck. Ummm. I learned how to wipe my own ass last week,” he guffaws (the joke is later reprised several times). His preferred way of starting an answer is “I dunno”.

Two sides coexist in the DeMarco universe: one laid-back and sunny, one more introspective. A casual listen to the album doesn’t immediately reveal the ruminations within: the music sounds upbeat and melodic, there are odes to love (inspired by his long-term girlfriend), guitars twang serenely. Yet, DeMarco’s father looms large throughout. In opener My Old Man, DeMarco sings about becoming more like his father – “Uh-oh, looks like I’m seeing more of my old man in me” – a relatable-enough sentiment, made more touching by the knowledge that his father is an alcoholic and an addict whom he hardly knows.

Born Vernor Winfield McBriare Smith IV in British Columbia, Canada, DeMarco was brought up by his mother, Agnes DeMarco, who changed his surname after his father refused to pay child support. “I’ve been trying to not turn into him. That’s the last thing I’d like to do, since I was a young kid,” he says. “But it’s funny when you look, and you go, ‘Ohh look, you do like drinking a lot now too, huh? OK, OK, OK.’ So it’s, uh, interesting.” In the song, he sings: “Look how old and cold and tired / And lonely he’s become… There’s a price tag hanging off of having all that fun.”

Nevertheless, he warns against taking this too literally. “Anytime I see myself becoming something that I don’t necessarily agree with, that’s kind of what I’m talking about there, I guess,” he says. “But that can be taken in several different ways. Take it like a trope or whatever. It doesn’t matter – it’s a pop song.”

The album was written months ago, when his father had become very ill: the last song goes: “The thought of him no longer being around / Well sure it would be sad but not really different / And even though we barely know each other / It still hurts watching him fade away.” Although his father’s health has now improved, the two are still not in touch. Did exploring these issues on the album change the way he views his father? “Um, no. I mean, I was trying to understand it. But I don’t know, I really don’t. It just solidified [the fact] that I don’t understand.”

A much happier relationship is with his girlfriend, Kiera McNally. They met aged 14, got together five years later, and are still together seven years on (“almost eight”, she chirps in the background). The album’s love songs are varied – some are about past fights (“I never meant to make her cry”), some about fluctuations of affection (“sometimes my heart may seem awful cold”), one harks back to the feeling of “seeing her for the first time”, others are inspired by emotions from the distant past.

Considering that a lot of music is about break-ups or falling in love, is it harder to find inspiration in a contented, settled relationship? “It still comes,” he says. “I think that just being in love – being out of love, being in love, being confused by love, wanting love, not wanting love, being scared of love – it doesn’t matter which. There are so many things better than feeling nothing at all. Long-term relationships are like a fucking mountainscape, you know? Things go up, things go down. That’s the fun of it.” What’s his top relationship advice? “Be kind. Be respectful. And be real.”

Facebook Twitter Pinterest Mac DeMarco crowdsurfs during his gig at Glastonbury, 2016. Photograph: Ekaterina Ochagavia/The Guardian

DeMarco’s personal life is a source of boundless fascination to his army of young fans. Back at Nambucca, Kiera gets several cheers, and audience members ask about his mum, Agnes, (who has developed something of a cult following online). Numerous Reddit threads are dedicated to speculation about aspects of his life: whether he and Kiera are still together, whether he takes drugs, and if so which ones. Does that bother him? “It’s fine. I mean, as much as they think they’re invested in my personal life, the reality is they’re not. They’ve seen pictures of my girlfriend, they’ve talked to my mom on Facebook – it’s not exactly knowing you, but it’s cool. My mom’s really excited because she loves talking to people.”

DeMarco has always railed against the “cool guy fantasy” of rock stars being separate from fans: “the idea of that sexy guy in the band, dark and tall and handsome, looking at his shoes like, ‘Don’t talk to me’ – that has been so unappealing to me for ever.” Most of the fans he encounters are excitable young kids, with the occasional surprise. “It’s always weird when someone takes their pants down and has a drawing of me tattooed on their butt. That’s happened a couple times.”

But he also likes to throw curveballs about his life into the mix: he told one interviewer that Kiera has sadly passed away; he informed an audience they had broken up. Recently he said in an interview that he had become a father, prompting family members to get in touch to congratulate him; his mother said it almost gave her a heart attack. “The whole thing with the internet,” he says with a groan, “it’s the wild west. People read into things too much – it’s all horseshit and I like to treat it that way and have fun with it.”

I understand how fucked up the youth is now, where your online life is equal to your self-worth – it’s so twisted

On 2015’s mini-LP Another One he read out the address of his flat in Brooklyn so fans could stop by for a cup of coffee, and over the next year “a couple thousand” people came to visit. “We made a lot of coffee,” he says. “A couple times people kind of overstayed their welcome a little bit, but for the most part they were just nice people. My girlfriend didn’t like it, neither did my roommate. I mean, they were game for a while but it gets crazy.”

He’s unlikely to repeat the experiment in his new place. He has just bought his first house, which made him feel “kind of weird and old”, after moving from New York to Los Angeles last August (“No real reason why – it just seemed a happening place, so it was like, ‘let’s go give it a shot’”). Now that he’s in LA, has he started to see the appeal of yoga and juice cleanses? “Nah, I don’t think so. I don’t like a juice, I like a smoothie, I like the chunkiness – a smoothie is halfway to a milkshake, and I’d have milkshakes every day if I could.”

It isn’t easy to get a strong opinion out of DeMarco, prime purveyor of contemporary slacker rock (in terms of sound rather than work ethic). What makes him angry? “I don’t get genuinely angry very easily. I don’t know. A whole number of different things. It’s hard to pinpoint what.” I try to stir him up a little. What does he think of life under Trump? “A lot of people are really put out, sad, disappointed… but I dunno. It’s not that it’s not my place to talk about American politics, but it’s a little complicated.” How worried is he about nuclear war? “If we got nuked I’d probably be fried before I even noticed it, which would suck, but would I know? Hopefully nuclear war doesn’t happen, that would really blow ass.”

The only stage at which he gets close to losing his cool is at the gig at Nambucca. A fan has climbed on to the stage, more people pile on, and DeMarco encourages the raucousness. Then one girl takes a selfie, then another. Then another. He politely asks her to stop but she is undeterred, pouting away into her camera; eventually he clears the stage. If someone wants to take a photo of the gig that’s fine, he says. “But when they come up on the stage and wanna do it, it’s like, you’re right here with me – stick to real life instead of taking a fucking photo to send to your friends.”

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How does he feel about social media? “It’s bizarre, but I understand how fucked up the youth is now, where your online life is equal to your self-worth. Kids have been led to believe that the number of likes you get on a post or something is equal to your popularity or how cool you are – it’s so twisted and evil. It’s really fucked up and scary, and it’s getting scarier.” He does have Twitter and Instagram accounts but rarely touches them; one of his most recent tweets, from last October, simply reads “#jarjarbinks”.

Social media has also meant that footage of his wilder live shows – nudity, drinking, a notorious incident involving a drumstick – live on online. “When those kinds of things happen it’s usually because I’ve had an off show,” he says. “What I try to focus on is try and play as well as I can and make sure everybody’s happy.”

It has just been announced that later this year DeMarco will be co-headlining eight shows in the States with psych-rockers the Flaming Lips, who approached him after playing some festivals together. Led by Wayne Coyne, the band are known for their euphoric, visually extravagant live performances – what will their joint shows be like? “It’s gonna be crazy. They’ve got their props and insane lights and bubbles and all that stuff. We’ll see what happens.”

Until then, does he have any pearls of wisdom to impart? “Nah, I’m good,” he says. “Just tell everybody to brush their teeth twice a day – keep it fresh.”

Mac DeMarco’s album This Old Dog is out now on Captured Tracks. He plays two sold-out nights at the O2 Academy Brixton, London SW9, on 30 and 31 May