I meet Japandroids, appropriately enough, in a bar. Soundcheck completed, Brian King and David Prowse are acquainting themselves with the barman's Margherita skills; "Not too bad" is the verdict. Prowse is also on the hunt for change – annoyingly, the cigarette machine doesn't take notes – but King goes one better by furnishing his bandmate with one from his own pack. The mood is light and playful, as well it should be. Second album Celebration Rock has been even more rapturously received than debut Post-Nothing and their globe-trotting success continues apace. Having appeared a numerous festivals this summer, this is the second date of an extensive European tour, their diary showing precious few free days between now and the festive season.

Vices sufficiently sated, Prowse and I move to the still closed venue. The faded ballroom splendour of Sala Apolo, bathed in blood red light, is eerily silent. Empty, it's remarkable how cavernous it seems, and it's a measure of how they're now regarded that it's packed to the rafters by the time they walk on stage two hours later. This is their first stand-alone show in Barcelona and, as Prowse explains, they're genuinely excited. "To us, Europe is still like unchartered territory; the only two times we've played here [Spain] have been at Primavera Sound. Those shows [2010 and 2012] are two of our personal favourites of all time, especially the first one – it was just so memorable. We've been dying to come back to play more clubs and see more of the country, so I'm really looking forward to tonight. It should be fun."

Of course, all of this so nearly didn't come to pass. Sick of slogging it out on their own and seemingly getting nowhere, they were ready to throw in the towel, leaving Post-Nothing as a valedictory last hurrah before calling it a day and moving on to something new. "The band was in the process of slowing down and coming to a halt right after we recorded Post-Nothing but before we'd put it out; and it looked like we were gonna be self-releasing again, like we had with some of the earlier EP's. We were still playing around Vancouver and had developed a bit of a small following, but nobody was really interested in helping us, or organising larger tours. At that point we weren't even getting offered many shows or anything like that, and we just felt that although we'd done a lot of cool stuff it was getting a bit disheartening. We even had our last show lined up, which was going to be CMJ."

So what changed? "We basically had made plans to stop being a band, but hadn't actually got around to stopping; and by the time we were thinking we were gonna be stopping, it was right when things started picking up. All of a sudden there's this label, Unfamiliar Records, who want to put our record out, Pitchfork are writing about us, there are opportunities to tour and so on – those were things we'd been waiting on for quite a few years. So as soon as they started happening, we were like 'Of course we're not gonna break up now.' We quit on quitting."

Anyone remotely associated with musicians and bands will be familiar with the heartbreak and struggle they regularly go through to 'make it', but Prowse doesn't recount those dark days as some overly dramatic reaction to not making any headway or remaining unsigned. According to him, it wasn't so much a case of abandoning their dreams of making a career out of music as not having those dreams in the first place, an ambivalence common to their home city. "Vancouver is not really a place where people are making music in the hope of becoming a 'professional band' as it were, it's something that you're doing because you love it, and more for purely artistic purposes. There's not a lot of grand aspirations, so what happens is, a lot of musicians play in bands for a couple of years then kill it and start something else. It's common for bands to go for a while then end, and do something new –explore different music, try something else, or add a new energy to their sound."

Humble, unfailingly polite, and genuinely grateful for the situation they find themselves in, Prowse and King come across as the ultimate music fans' band – regular guys who are just as passionate and informed as the people who squeeze to the front at their gigs and belt out every word to every song. Prowse recalls the awkwardness when, as things started to take off, fellow Canadians Frog Eyes were booked to open for them, a band they had idolised and paid to see countless times as students. Success, and more pertinently fame, just doesn't sit easily with them, something they've been slow to come to terms with. "Just living this life in general is a gigantic surprise still, for me. It's hard to wrap my head around that this is actually my real life. It's incredibly surreal, but it does start to become a bit more normal. You start getting used to the routines of touring, to the fact that you're gonna fly over to Europe and tour for a couple of months – those things start to seem a little bit less absurd."

One way in which they remain grounded is an absolute refusal to get carried away, and to live each moment for what it is – there's no pretence to grandeur or sweeping statements of ambition, just a simple focus on the fact that there's another gig, and another set of loyal fans to perform for. Prowse agrees that such an approach stems from how close they came to splitting, and recognition of the fickle nature of the public's tastes.

"We never had a grand plan for the band and I think that's a really good thing for us in the sense that we still view everything that comes as a bonus, because to some extent, it feels like this band has been on borrowed time for quite a while. We'd already made peace with the fact that we weren't gonna keep going, and yet it has kept going for another four years since. Everything is viewed pretty short term, and we still have that mentality where we don't really assume that we're gonna get to come back here again; if we do, it would be wonderful, but right now this is it, this is our chance to play Barcelona and do it right. It's a very positive attitude to have in the sense that it helps you take everything a bit more seriously and hopefully also gives you pause to enjoy what your doing because you think about it in terms of 'This is my opportunity to do this, so I better make the most of it'."

Making the most of it is a theme that crops up regularly during our conversation, and it's clear that this idea, in part, fuels the joyous abandon with which they approach their art. Both albums are a head rush of full-on, intense rock'n'roll; King's thick riffs and drumming that demands to be pounded on whatever surface you happen to be near propel songs about drinking, girls, and parties. It's a musical distillation of 'Live fast die young' coupled with 'No regrets', and I've often wondered if part of their energy is derived from fears that it could all end tomorrow. Are they, perhaps even subconsciously, in a rush to get everything in their heads out in to the world? Prowse is not so sure.

"It's really hard to understand your motivations. That idea of making some kind of conscious decision about 'This is the kind of music we're gonna make', for us at least, didn't really happen; we had those conversations and just ended up making stuff that was completely different from what we talked about. The music comes very naturally from the way we like to play; for me, when I play drums, I wanna naturally play fast and I wanna play really loud. That's just the most fun for me, and it's been interesting to try and go beyond that and write slower songs now and again, like 'Continous Thunder'."

Those familiar with that particular track will recognise that it's a long way from ballad territory – "a mid-tempo rock song" as he puts it – but it is "slow for us." He goes on. "It's just very natural for us to write those kind of songs and as we go along, we've really embraced the music that we're good at. If you listen to our early EP's, it's a bit more all over the map, but there's still that same sense of urgency and nervous energy to them. We're cultivating a bit more of our own sound, in my mind at least; it's a bit more distinctly us, and a bit less a scattershot of attempts to do different types of songs."

It's remarkable that, after only two albums – both of which contain only eight tracks – they've developed a sound that is instantly recognisable. Despite using the same set up and personnel, Celebration Rock sounds more expansive; louder and clearer, yet with the same reluctance for over-dubs. Likewise, lyrically they've made a quantum leap forward, and gone is the simple sloganeering and repetition. King has mentioned before in interviews how hard they work at being creative, how it can sometimes take a month of graft before being happy with a new song, and Prowse is quick to point out that their gratitude comes not just from appreciation of their own success, but from feeling bad for those artists for whom it eludes.

"I'd hate to ever sound ungrateful because this is something you dream about, and we have many friends back home making really wonderful music, very talented people, and they're not getting the same opportunities that we got. This whole thing is pretty arbitrary in a lot of ways; there's so much great music constantly being made and sometimes really good bands get exposure and people hear about them, and sometimes really good bands just totally slip under the radar. And obviously, sometimes really terrible bands all of a sudden become really popular somehow…"

He declines to name any offenders, but is eager to discuss those he feels "don't really get their due." For whatever reason, bands like Apolo Ghost – "the best band in Vancouver" – and Frog Eyes just haven't caught the same breaks; luck, it seems, does play a part. "I think we're pretty good. I mean, if I thought we sucked, I wouldn't be playing in the band every day, but I also think we're very lucky – I'm very aware of that." Like many bands who seemingly sprouted from nowhere they owe a debt to Pitchfork, who championed them repeatedly back in 2009 and awarded their debut a coveted "Best New Music" tag. While traditional publications, and the media in general, have seen a decline in their influence regarding new music, it seems that Pitchfork's continues to grow, something Prowse is happy to acknowledge.

"Pitchfork getting behind us was an obvious kickstart and was a huge catalyst for what's happened with us. We'd gotten a little bit of hype here and there from a few blogs and local papers in Vancouver and stuff, but when they wrote about us...that website is just so incredibly powerful, and when people read about bands there, they are gonna go check them out. I do it too; if I hear about a new band one of the first things I do is read their Pitchfork review. It's just my automatic go to, and I can't help it 'cause it's just such an obvious way to find out about a band."

It's curious that with hype settling around so called "post-internet" artists, and the acclaim afforded to the likes of Grimes, Alt-J, and Purity Ring, their old school, back-to-basics approach has struck such a chord with people. With much guitar music, especially rock and indie, being fashionably dismissed as derivative and boring, Japandroids have been embraced like no other, and Prowse is certain as to why. "My presumption for why our band has been able to build on that initial buzz is because we put on a good live show, basically. We write and play the kind of music that's a really fun release for people, and I think it's precisely because there's not that many bands making positive, high energy, rowdy rock'n'roll. There's just not as much of it happening right now, so it's a little easier for us to stand out. We hear a lot of stories from people saying 'When I heard the album, I listened to it non-stop for the entire summer,' or they'll tell us 'I put on your music when I'm not happy, so I can feel better.' They [the albums] are like the soundtrack to basically having a good time and just letting loose."

There's certainly plenty of that when they take the stage. "We're Japandroids, and we're from Vancouver, British Columbia, Canada. We'd like to play some songs for you if that's ok" announces King before launching into 'The Boys Are Leaving Town'. With a tightness bordering on telepathic, for a little over an hour we're treated to a roller coaster ride of hands-in-the-air, feel good, sing-along rock. It's impossible not to be swept away by the sheer energy they bring, King careering round the stage while Prowse batters his kit into submission. It's hot, noisy, and everyone from the multitude of stagedivers to those grinning insanely at the back look like their having the time of their lives. Exhausted, and drenched in sweat by the end, the duo look satisfied with the mayhem they unleash, and I understand now what Prowse means when he says "I think our albums are made almost as advertising for our live shows, to wrangle people into coming to see us."

"I don't really know if we even meant to do this, but people like to sing along and really immerse themselves in the moment at our shows. You know, I've been to so many concerts in my life, and that just does not happen very often at all. Especially with a band that's not that popular. I mean, it's one thing if you're an arena rock band, or Bruce Springsteen, but it's pretty weird when you play to a club of maybe 200 people, and everybody is singing every word. That's very rare, and I can't even think of another band that I've seen recently where that happens."

Having seen first-hand the effort the put into their shows, the punishing schedule they're happy to accept becomes even more impressive. Touring, particularly by road, can be a drag; surely it's harder to do with just one other guy, especially when he's one of your best friends? "It's hard for me know, as I've never done this with another group of people," reasons Prowse. "This is all I know. But I think everyone goes through the same shit; people get tired and frustrated, as you naturally would when you spend an absurd amount of time together and in close contact. But at the same time, you develop this really strange bond that is hard to explain. We've had friends come on the road with us before, for four or five days, or people from our record label will come out, and they start to get it, but even for them, for people who are involved in music on a day to day basis, they don't fully understand what your life is like when you do this. It's pretty hard to explain to anybody who hasn't actually lived it."

You get the sense that they genuinely relish performing, and despite complaining "how nomadic it is, and how much you completely lose touch with any sense of home," the trade off of getting to "go play festivals in Japan, or Australia, and seeing awesome places like Zagreb" more than make up for the sacrifices they make. Prowse saves his scorn for those who see the hard miles as a chore, not a privilege, and spend their time holed up in the studio. "We've met a lot of bands that are very jaded and very cynical about touring, who view it as something they just have to do to pay the bills and promote the record. It's never been like that for us, and if it ever got to that point, we just wouldn't be a band anymore. I think that's so awful, and so disingenuous when you see a band play to couple hundred people who have all paid money, and been waiting for this for who knows how long, and they look miserable on stage like they're just going through the motions. That's the most depressing thing I can think of and I when I see that, it just makes me never want to listen to that band ever again to be honest. That's a fate worse than death and just so sad; I mean, you're doing this because you love to do it, and if don't love doing it anymore, then just stop."

Fortunately for us, stopping is not on their agenda; not anymore. After this tour there are plans already in place to start thinking about another album, and they're reluctant to rest on their laurels. One thing they're not contemplating however is expanding their sound with extra musicians; not for them the Black Keys route of collecting producers, guitarists and keyboard players. "We realise there are limitations to being a two piece but at the same time, so much of our identity is locked up in that fact, and when you've been doing things just the two of you for so long, it would be really strange to involve someone else in the equation. It would be really hard to find somebody who could fit and make it work. I completely understand why bands do expand - they get bigger and maybe feel pressure to expand on their sound – but for us, we both feel there's still plenty of room to move forward with the sound. We can keep pushing ourselves to achieve more and improve without the pressure to have somebody else on stage."

With that, he's off; to raid the rider and find his bandmate. Theirs is a peculiar story, but one to restore faith in the notion that hard work and perseverance can pay off. Their previous life may have evaporated, but even up there, on stage, you recognize them still as one of us. With the wide-eyed enthusiasm of a child on Christmas morning, is easy to believe him when he beams "It's really exciting to live this life, and do things we never, ever dreamed of." They want us know that we can all love with a legendary fire, no matter who we are or where we come from. Celebration rock indeed.