Sigur Ros are ready to surprise, baffle and delight again. The Icelandic band – one of their country's most successful exports, and the second most popular musicians after Bjork – are readying to make their first album in five years.

Founder Georg Holm, who has been a key part of the band since their beginnings in Reykjavik in 1994, is ready to record a "fantastic" comeback album: but first a European tour, which takes in two nights in Glasgow, beckons.

Initially the plan had been to tour and record – Holm, resting at home after a long year of touring in the US and Asia – laughs as he explains how that plan fell apart.

"It's really difficult to record a new album," he says. "We had this really great idea of working on new music whilst we were on tour. We were going to write and record everything for the new record on the road – but we have given up, basically. We have decided we are going to finish this tour and then early next year we are going into a studio and we are going to finish it. We have a lot of songs, and we are playing them. We need that extra push to make sense of the album itself. It is going to be fantastic, it just needs time."

Holm cannot quite believe his band's longevity and he's surprised that their ethereal soundscapes have proved to be so resilient. It was 1997 when the band, who create a swirling, miasmic, melodious and shattering sound, emerged from Iceland.

He adds: "I guess those early years are a blur now. There has been many years of going to the studio, working really hard to make a record, and then straight on tour for a long time, and then when the tour finishes, a month's break and then back in the studio.

"I guess we have slowed down a little bit, but that is natural, we are not getting any younger and we all have families and outside interests. Maybe it was a little bit much, and we needed to cool down a little bit. I hope that leads to a good effect on the next record. We are all feeling that we want to do something absolutely amazing. We want to do something with the next record which is spectacular."

Sigur Ros, at their best, create an immense, momentous sound: drifting clouds of glistening music led by lead singer Jonsi Birgisson's sweet, often wordless, falsetto. A band that is often described as post-rock can, in their pomp, sound closer to pre-apocalypse.

It is a sound which is adored by its fans across the globe, some more famous than others – the band have been championed by Brad Pitt and Gwyneth Paltrow. Their music has featured in films, documentaries and Game of Thrones, soundtracked sporting broadcasts and inspired imitators and encomiums.

Holm is principally a bassist but as with the rest of the band he plays several instruments and he has been with the band since their beginnings.

2013's Kveikur was Sigur Ros's first record as a three piece, after the departure of long term keyboardist/strings composer Kjartan Sveinsson, and surprised critics with its aggressive edge. It seemed there was trouble in the band's usually soft-focus paradise.

The new album, Holm says, takes on some of that album's abrasive edge (Kveikur means fuse, or candlewick) but also harks back to their early albums such as the breakthrough Agaetis Byrjun, their third album, the unusually named (), and the successful Takk of 2005 (which featured perhaps their best known song Saeglopur).

The band have in the past been described as being monosyllabic in interviews but Holm is warm and amusing.

He says: "I think the new album will take elements of that last album. There are some good elements of Kveikur in there, aggressive and loud, but there are also, for me, almost nostalgic moments, going further back."

He adds: "There are new sounds. I think it is a good mix of atmospheres that is coming out of us at the moment. But we shall see, once we get into it, and put everything we have in front of us. Then we will know better what we have. At the moment it is a bit scattered. We have loads of ideas, and haven’t had the time to sit down and play them through, and contemplate them. We need focus."

Holm says beauty is never far away from their composition, however edgy the last album sounded. He says: "I think we all like the energy of when we play something aggressively, you look at your instrument like a hammer rather than an instrument. It is like a tool almost. But we all agree in this band that music is not just atmosphere, it has to have an element of musicality to it, it has to have melody, and melody is usually beautiful. And Jonsi is definitely a genius at doing that. His vocal melodies are amazing."

Jonsi is known for singing both in Icelandic and Vonlenska, or Hopelandic, a form of glossolalia, or constructed language which provided the lyrics for most of the mercurial album () in 2002.

Its use in their music has been overstated in the past – much of their lyrics are in Icelandic. For Holm, their songwriting is about entering "the zone", where the music is completely overwhelming (for fans, this is a familiar feeling).

"We do get swept up in it too," he says. "That is kind of what I hope for anyway. There can be elements that ruin it for you, something technical on stage, or something in the room that tears you out of that moment. But definitely when we write the songs it usually is finding that moment, when we know we are doing something correctly, when we go ‘Wow, that was amazing’. And then, when we play it live, that’s what we hope for, again. It is a really nice feeling when you are playing, and you zone out. Sometimes it happens only a few times in a show, and sometimes it is every song where you think ‘this is amazing’ or ‘wow, I am great’ [he says laughing]."

Sigur Ros are playing Glasgow's SEC Armadillo on September 24 and 25 and Holm says the band are happy to be performing in Europe again.

He says: "I think we always try to reinvent ourselves, and when we go and try and make a record. Every time we go on stage we try and reinvent it. For this tour we decided we wanted to change things, so we worked on the songs a lot, so that although they are the same songs, there are elements that are different. I think because of that, it always feels fun and fresh."

In those 20 years, Sigur Ros have to some extent become part of the world's view of Iceland. Their ethereal and explosive sound can be linked readily to the country's wild landscape. But, as the band has changed, so has the country.

Holm notes: "A few years ago, I heard that a big proportion of the people studying at the University of Iceland were studying Icelandic because of Sigur Ros! So we are definitely part of the exposure of Iceland. In good ways or bad ways, I don’t know. I hope it's good. It's nice too, for the lack of a better word, [to be] an ambassador for Iceland abroad. We are proud of that – we are Icelandic."

He adds: "I am not an old man or anything, but I have seen Iceland change. It is totally different from when I was a kid, especially as I have kids now growing up. But there is still a lot of freedom for the children for example. They just run around. If my daughter doesn’t come home from school, I am like ‘yeah, whatever’. I know she is with her friends – it is like that. It's kind of loose and free. But I have seen it changing a little bit – there is more violence. Reyjavik is becoming more like a big city. You can get stuck in traffic now!"

But Iceland's influence remains, as the band ready themselves to create their eighth album. Holm says: "I have thought about it quite a lot. I think the surroundings have to affect us. This is where I live, it must have had some influence on me as a person – and then what I create. There is no doubt about it."

Sigur Ros are playing Glasgow's SEC Armadillo on September 24 and 25