San Francisco Frontiers - Polka-dots and hypnotic riffs fuel viral duo Angine de Poitrine

Clad head to toe in black-and-white robes -- their faces hidden by outsized masks -- the duo are known only by pseudonyms, as the "time-travelling explorers Klek and Khn".

On Thursday night the duo played the latest in a series of booked-out concerts across Europe, at the hip Botanique venue in Brussels, with a long list of US dates lined up through summer.

Pumping out an experimental mix of syncopated guitar, bass and drum loops somewhere between techno and acid rock -- their trademark sound is dissonant and "microtonal", which means they play the notes in between the notes.

"They're such a party!" said Clara Moes, a 24-year-old fashion student who, like many, turned up in polka dots for the occasion. "It's like they came out of nowhere -- their characters are so mysterious."

The moment the tickets went up online, "sales went through the roof", said Olivier Vanhalst, the Botanique's programmer -- who says the band's unique appeal is still something of a mystery.

"People are drawn to the live experiences, a sound like none they've heard before, the mystery and the costumes," he said.

Formed in 2019 in Saguenay, in Canada's Quebec region, the band's name is French for angina pectoris -- a kind of chest pain that can signal a heart attack -- in a nod to their art's absurdist bent.

They started out with help from the CEM experimental music centre in Saguenay, where a group of aficionados work to support niche musical forms.

The ride to fame started back in February when US radio station KEXP published a video of them recorded at a music festival in Rennes, in western France that racked up 15 million views in three months.

"It's just wild," Jean-Louis Brossard, the Trans Musicales festival's artistic director, told AFP. "It really shows there is space for music that's different, that's not mainstream."

- Secretive mystique -

On stage, neither of them speak -- except for an occasional war cry -- as they perform fully-masked in the stifling heat of a Brussels spring heatwave.

Khn simultaneously plays guitar and bass thanks to a double-necked instrument with a looping system to layer riffs one on top of the other.

On the drums, Klek holds the heady rhythm as his giant protruding nose bounces to the beat.

Concert-goer Peter Somers, 59 and wearing a regulation polka-dot shirt, came across the band's "bizarre" music online.

"It's so refreshing -- this is not something you can create with an algorithm and AI," he said.

After a first album "Vol.1" in 2024, the duo just released a second -- six tracks spanning 36 minutes and a vibe ranging from the manic "Mata Zyklek" to the gypsy whirlwind of "Utzp".

After a handful of early interviews, the pair have stopped speaking to the press -- gunning instead for a secretive mystique, in the vein of legendary French duo Daft Punk.

But beyond the gimmicks, the music has drawn rave reviews from fellow musicians including Foo Fighters founder Dave Grohl, with critics seeing influences from jazz to the US counterculture icon Frank Zappa.

Will they prove more than a flash in the pan? The Trans Musicales' Brossard says it is too soon to say -- but that, for now, "the crowd response is pretty amazing".

Q.Taylor--SFF