SIMON Neil is explaining why he’s a romantic.

Not, I should perhaps make clear, in relation to his partner, even if the song Re-arrange on Biffy Clyro’s new album is basically an apology to his wife for some of his behaviour when making the record.

No, the romance he’s referring to is about how the band look at music, and the way they write songs.

“I know that makes me sound naive, but I’ve got a romantic attitude towards music,” says Neil. “I don’t want to ever write songs with a career in mind. I want things to be pure and honest, and the people that have tried to take things from us, you can understand they’ve never written a song in their lives because if they had, they’d realise that they were trying to basically take a piece of my body away.”

Those people are part of the somewhat turbulent road that Neil and his Biffy bandmates – Ben and James Johnston – have taken to making their new record, Ellipsis, which is released on Friday.

Their first record since 2013’s Opposites is comfortably the most varied in the band’s career, and one that’s angry, melancholy, celebratory and even tender.

The anger comes from some of the characters that have drifted into Biffy’s life in recent years, as the Ayrshire group went from talented King Tut’s regulars to Scottish cult heroes and then all-conquering rock gods. They will cap this summer by headlining the Reading and Leeds festivals and having a massive homecoming show at Bellahouston Park in August.

Yet as the band became bigger and bigger, the circle around the band expanded too, and not for the better.

“When it’s just me, Ben and James we get s*** done and it’s like we’re teenagers again,” says Neil. “What annoys me is that when a band gets big there’s always people sticking their heads in, when they’ve never written a song in their lives. They try to take things that belong to you because you’re now playing big shows and I guess it’s just human nature for people to want a piece of something that’s going well.

“But I can’t believe how people will lie to your face, pretend they are there for you and with you, and as soon as your back is turned they will undermine you and try to f*** you over. Sadly we’ve found that with different parts of the band and in my personal life in the past couple of years.

“Maybe I was naive and took people to always mean what they say, but we’ve had to part ways with people who’ve ripped us off and f***** with us, and a couple of these songs are about the fact that the only people who know about this band are the three of us.

“We started Biffy as teenagers, it’s the only band we’ve ever been in, so don’t give us your opinions now. You don’t live it, you don’t breathe it and at the end of the day if there’s money to be made elsewhere then you’ll go there, but we’ll still be with this band.”

His words might bubble with fury, but Neil is as relaxed an interviewee as you could hope to speak to. He chats freely and openly, enjoying the calm before the storm that’ll occur when Ellipsis is released. After finishing our chat he’s off to watch some of European 2016 while relaxing with friends and family.

The recording process wasn’t nearly as easy.

The singer’s frustration at discovering that people had been ripping them off soon turned to depression, borne out of a horrendous personal period that saw several friends and family of the band, including his gran, pass away.

Sitting down to write songs, he drew a blank. It was a temporary move to Los Angeles and writing songs for a solo project (called CCZ and due some time next year) that helped the 36-year-old snap out of his rut and begin writing for Biffy again.

However, this is a different version of Biffy than before. Their previous six albums can be spilt into two distinct trilogies, with the first three providing abrasive noise and the latter trio delivering a hefty stadium-friendly sound.

This time the plan was to have no plan.

“On the last three albums I was visualising concepts for each record, so on Opposites or Puzzle I wanted them to be one journey, without any sharp left turns,” explains the singer. “With this album we just picked the best songs and weren’t worried about making it a complete piece of music. I think we wanted to liberate ourselves from feeling that every song we do has to be a rock song, and it was quite nice to embrace different elements in the studio.”

That shows throughout Ellipsis. Small Wishes is a country twang of a song that Neil reckons sounds like a pub sing-a-long. Friends and Enemies features a children’s choir, and Re-arrange a sleek pop tune tapping into the band’s passion for hip hop.

“To me, Yeezus [by Kanye West] is one of the most important records of the last 10 years,” argues Neil. “What annoys me a little is that there’s always amazing rock bands out there, but sometimes I’ll hear a rock song on the radio and it sounds so flat and unthreatening. Then I’ll hear Beyonce, and that will sound edgy and threatening, with creative lyrics.

“Rock was always meant as something that would scare folk, and not being part of the status quo. It’s about pushing the anarchy levels up, and I feel there’s a fear in rock music now. It’s about making records like AC/DC and Led Zeppelin, and we’ve tried to do that ourselves on the last three records, but we can’t constantly look back at records 40 years old.

“Some of those songs on Yeezus, they’re so brutal, so punk rock, and why does that sound more extreme than 90 per cent of the rock records I’ve heard? I’m not saying our record is the one to change things, but we do have a hunger to push things forward and tweak what we do.

“Risks can be taken in all music and rock music has been too slow to push the boat out in the last few years. Let’s make music to piss people off and that our parents don’t like – and I know I'm too old to be saying that.”

Ellipsis is therefore very much a studio album, where the band have experimented as much as possible. They were aided by producer Rich Costey, while the creative process involved building the songs up in the studio.

“Half the songs we didn’t play in the practice room, because we didn’t want to get bogged down or go into a default setting as a rock band,” he explains. “Rich brought a real grime to this album, where we were putting my guitar through synthesizer pedals, and the drums through guitar amps. With Garth [Richardson, who produced the last three albums] it was militaristic where we’d knuckle down, record something and move on. There wasn’t much creativity happening, whereas with Rich it was like the studio was the fourth member of the band.”

For all of Biffy’s new-found studio love, they remain, at heart, a band who thrive best in a live setting. Their headline shows at Reading and Leeds mark the second time they’ve been asked to top the bill there, while their Bellahouston Park performance will be their biggest Glasgow gig ever.

It’s a status that Neil is now much more comfortable with.

“I used to get really nervous before big shows and have all this punk rock guilt about whether we’d accidentally ended up there. Now I believe we can create an intimacy in a big show the same as you can in a small show, you just have to manipulate it in a different way. Touring with the Foo Fighters or Muse made me realise any show is entirely down to what you make people feel like.

“When Coldplay play a stadium they manage to make people feel like they’re up in the clouds and it’s a joyous, spiritual Kumbaya, round-the-campfire thing. That’s not what we’re trying to achieve, but it shows how you can put your own stamp on a massive gig and I really admire those bands who’ve been doing it for years and years.

“I like the Dave Grohl thing where it feels very casual, like watching a mate’s band, but at the same time I want people to watch us and think: ‘Oh, they’re like superheroes.' The main thing is just to be who we are, though – I still talk absolute pish onstage, because that’s who I am.

“I’m not going to be Mick Jagger, but I’m the best representation of me onstage, and we’re not pretending to be anyone else.”

Ellipsis is released on Friday. Biffy Clyro play Reading and Leeds Festivals on August 26 and 28, and Bellahouston Park in Glasgow on August 27.