Image copyright Jabari Jacobs Image caption Twenty One Pilots: drummer Josh Dun (left) and singer Tyler Joseph

"I feel like we've got the coolest people listening to our music," says Josh Dun, drummer in Twenty One Pilots.

"The type of people who would call us out if we did something dumb. They'd know if we just phoned in a show or a song. They keep us on our toes."

These days, those toes barely touch the ground.

Twenty One Pilots have played 128 shows so far this year. On Friday, they begin the first of two sold-out nights at London's Alexandra Palace.

Almost by stealth, they've become the year's biggest breakthrough band.

The momentum began with Stressed Out, a rock-rap ode to the innocence of childhood ("Used to dream of outer space, but now they're laughing at our face / Saying, 'Wake up, you need to make money'").

Released in January, it reached number two in the US and gave the band their first UK hit. But things really took off when they contributed a song, Heathens, to Warner Bros' anti-superhero movie Suicide Squad.

Eerie and atmospheric, it took singer Tyler Joseph's prevailing concern - the demons faced by people with mental health issues - and applied it to the film's cast of villains and outcasts.

Since its debut in June, the song has been streamed more than 368 million times, arguably becoming more successful than the critically-derided film it hails from.

"I don't know about that," laughs Dun. "I enjoyed the film - we went and saw it opening night in Alabama with our crew. It was a cool thing, hearing our song in a movie."

Media playback is unsupported on your device Media caption Highlights from Twenty One Pilots' set at the Reading and Leeds festival 2016.

Unusually for a soundtrack submission, Heathens wasn't a cast-off or an after-thought, but a specially-tailored original.

"It was the first song we did for any sort of soundtrack, so we approached it the exact same way as we would writing a song for our own album," says Dun.

"Then, if they didn't like it or want it, we could use it for our next record.

"Luckily they loved it. We didn't have to make any changes or sacrifices, which was a really good feeling."

That stubborn refusal to compromise is the key to Twenty One Pilots' success.

They turned down record deals until their third album, resisted industry pressure to change their sound and acted as their own roadies long after they started selling out large venues.

It all stems from a manifesto they dreamt up in their early 20s, when the duo still lived with their parents in the mid-western college town of Columbus, Ohio.

"When I got out of High School, it was my mission to play music and I figured networking was the best way to do it," says Dun, filling in the band's back-story.

"So I got a job at a music store and became friends with this guy Chris who invited me out to a gig - and I loved everything about it, except I wasn't playing drums.

Image caption The band's name comes from Arthur Millers' play All My Sons, in which a businessman sells faulty airplane parts during World War 2, resulting in the death of 21 US servicemen

The band was an early incarnation of Twenty One Pilots. When Dun and Joseph met after the show, they instantly hit it off.

"We got together three days later and we stayed up all night talking about our visions and dreams," says Dun. "We were both very vulnerable. but we just opened up to each other.

"I remember talking about what we believe [they are both committed Christians] but also the concerns and doubts that we had in ourselves and how the industry works. We wanted to switch up the way people formulate a song, or put on a live show.

"I left that day feeling, 'This is a guy I want to be friends with for the rest of my life'. The music world seemed so big, but it seemed like something we could tackle, and tackle together."

The problem was that Twenty One Pilots still had a drummer, Chris Salih, the very same person who had introduced Dun and Joseph. When he left in 2011 citing financial pressures, Dun was immediately drafted in.

Soon after, bassist Nick Thomas also quit to attend college, and the band were forced to reshape their sound, with Dun triggering samples and backing tapes to flesh out their live shows.

The pared down line-up also indulged their eclectic musical tastes, incorporating elements of reggae, rap, rock and piano pop into their songs (the only genre they wouldn't touch is "southern American country", Dun says).

The results don't fit into any preconceived category - they're simply listed as "alternative" on iTunes - but it makes perfect sense to a teen fan base who've grown up in the anything-goes streaming era.

Image copyright Reuters Image caption The band have earned a reputation for dynamic and dramatic live shows

Despite that, the band were told to smooth out their sound for mainstream consumption. It's a topic they address on the single Lane Boy.

"They say, 'Stay in your lane, boy', but we go where we want to," sings Joseph as he plays, almost defiantly, the ukulele.

Later, he protests at the "heartless" songs on Top 40 radio, adding: "Don't trust a song that's flawless".

"I never want there to be a perception that music hasn't done anything for us," says Dun. "Music changed my life, and it changed Tyler's life. But there's also music that doesn't mean anything, and doesn't provoke any sort of thought or desire to get better - and that's something we both agreed that we wanted to talk about."

Accordingly, the band's current album is themed around a character called Blurryface, who is essentially the physical manifestation of Joseph's anxiety and insecurity.

On stage, he turns into the character by smearing black make-up over his face and neck - representing the suffocating effect of his neuroses.

Dun, meanwhile, has been known to play his drums from inside the audience, sitting on a platform held aloft by fans.

Image copyright Jabari Jacobs Image caption At the age of 12 "I walked to the music store every day and played drums," says Dun

They operate like a rock band, but neither musician plays guitar. Yet they seem to have stumbled onto a way to reinvigorate a genre which has languished in the doldrums for the best part of a decade.

In the US, where Billboard compiles charts for every conceivable sub-strata of music, Twenty One Pilots have soared in categories like adult contemporary, mainstream rock, pop songs, trendsetters and even dance.

"It's been real crazy," admits Dun.

"Looking back to when Tyler and I first met and started talking about what we wanted to accomplish, I feel like we're at a place now where we've surpassed even those dreams and visions.

"It's really cool... because there wasn't a second option or a Plan B."

Twenty One Pilots' latest album, Blurryface, is out now on Fuelled By Ramen. They play Alexandra Palace in London on Friday 11 and Sunday 13 November.

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