Europop is often exactly what it sounds like: a fizzy, sugary confection for hot days by a Malia swimming pool, trying to burn off the previous night's foam party. These songs revel in their own blitheness and, while they occasionally sound a melancholy note, they dare you to accuse them of having anything but the sunniest of dispositions.

Not so with Belgian pop star Stromae, whose tracks blend the corn-syrup pleasures of continental pop with tough lyrics about disease and the drudgery of work. But far from clearing the dancefloor, he's galvanised it. Two of his songs were in the top five biggest sellers in France last year: one, Papaoutai, fused Congolese rumba with piano house on a song about absent fathers, while the other, the ballad Formidable, imagined a drunk bum pathetically addressing a beautiful woman.

"I'm sure, ever since I was really young, that happiness is not a bottle of champagne and a girl and a limousine and a swimming pool," he tells me. "It was obvious for me to talk about real life, even if its not the thing we want to hear."

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Half Rwandan and half Belgian, Paul van Haver grew up rebelling from his classical music education in favour of hip-hop, but increasingly drew on the African music his parents played – an inversion of tradition that suits his stage name, a scramble of Maestro.

"Hip-hop, pop, dance – the common point is melancholy. That's international, and I like this word because it's not only about sadness or happiness – it's both at the same time. And that's human and that's life," he says in a melodious tumble of accented English. "The fact that I'm coming from Belgium helps me to be like that. Because we are known to be in the middle all the time, between Flanders and Wallonia – we say in French, compromis à la Belge, compromise like a Belgian." He says you can hear this as far back as Belgium's 1980s new beat style: "It's not really Afrobeat, it's not dance music, it's more downtempo. What kind of music is it actually? We don't know, but we dance to it. And that's the way I work in my music also."

Papaoutai is staggeringly powerful, as Stromae again compromises like a Belgian by palpably shifting from philosophical wondering to anger and back, all around the knotty issues of fatherhood. "I'm 28, and I have to have a baby now, in a normal way of life," he says, implicitly acknowledging that hundreds of millions of views of his videos on YouTube mean he is far from it. "As I say in the song: everyone knows how to make babies but nobody knows how to make fathers." Quand C'est, meanwhile, literally addresses cancer ("I talk to him: leave us, please, just go on holiday or something") while Moules-Frites uses Belgian's national dish as a metaphor for sexually transmitted disease, with its protagonist enjoying too many mussels – but not the kind you have with fries and mayonnaise.

Stromae's videos and live TV performances, made with graphic and fashion designers creating an aesthetic informed by MC Escher and Africa, have approached high art. For a performance of Papaoutai at a music awards show (featuring a cameo from a witless will.i.am), he adopted a cadaver stiffness with a grotesque smile, so immobile he was carried on stage like a prop; for a TV performance of Tous les Mêmes, he made one half of his head female and the other male to act out the quarrelsome couple in the song, even conducting an interview with Eurotrash's Antoine de Caunes as the pair.

"It's about cliches in the relationship," he explains. "Of course he's rude, because that's the cliche of a bad man in a relationship, but the girl is stupid also ... It's just a fight between a man and a girl, which is lovely, beautiful – that's love, actually." For the video to Formidable, he set up hidden cameras in a busy street, then acted drunk as he staggered around singing the song and attracting the attention of the starstruck police.

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This play-acting is the opposite to the Adele school of pop, where realness rules, and Stromae has learned it from the French greats. "Piaf, Aznavour – I'm a fan of the old generation, and the way they act on stage. Am I trying to be myself? No, just doing my job, which is acting characters from real life. To personalise the work or think that it's your life … Your life is not interesting – talk about a vision more than that." He says this drama stems from intense, day-to-day shyness. "You have to express everything that you kept in all the time when you are so shy in your social life – you have to go on stage and do something totally ego trip, megalomaniac, the opposite of your everyday personality."

Back and forth he goes: shy, bold, angry, happy, sad, shy. "Who do you want to be: the radical man who can make a choice in one second, or the man who never takes decisions?" he wonders. "That's the question: who's the best? Actually, there is no best. I'm more the kind of man who never makes decisions. But impulsivity is not the opposite of courage; I think it's possible to do both. Maybe I'll find another way of doing a compromise." Spoken like a true Belgian.

Stromae's second album Racine Carrée is out now on Universal. He plays Koko in London on 20 February as part of an 80-date European tour.