ALTHOUGH clad in the uniform of the modern alt-rocker - black skinny jeans, black Doc Martens, black hoodie - Sam McTrusty is not long back from competing in the Dunhill Links, the pro-am golf tournament played every year on the Old Course in St Andrews, Kingsbarns and Carnoustie.

Compared to his day job, it felt like a trial. "I was shaking," he says of partnering English pro Simon Khan over three rounds. "I'm standing next to Rory McIlroy on the range and we're both hitting shots. Then there are 400 people watching me hit from the fairway. I was more nervous than I've been playing any gig - and I get really nervous before gigs. I can't eat. I can't stand still."

Such are the opportunities that come your way if you're prepared to graft. And graft, as we will discover, is a key ingredient in the inexorable rise of the group McTrusty pilots, Twin Atlantic. Likewise the game of birdies and bogeys, which is why we're in The Golf Lounge in Glasgow, as low-risk an environment in which to swing a club as any at this time of year.

The singer and guitarist, mildly hungover after a late night at a casino, sits alongside his fellow 26-year-old Ross McNae, with whom he grew up on Glasgow's south side. Twin Atlantic recently released their second full-length album, Great Divide, the follow-up to 2011's Free, which went silver with more than 60,000 UK sales. The new record might surprise some followers, evoking as it does such rock behemoths as Def Leppard and Big Country. This week the group embark on a European tour which kicks off with a show in Aberdeen on Thursday and a brace of dates at the Barrowland in Glasgow, which sold out within hours of going on sale.

Beyond a barrier to the side of our table, sinewy drummer Craig Kneale, 28, gamely attempts to use right-handed clubs (despite being left-handed) under the watchful eye of lead guitarist Barry McKenna, 29, who at his peak played off a handicap of four. We would have been here a week previously had McTrusty not received a call inviting him to the east coast, but who can blame him? "Make hay while the sun shines" will be a recurring theme today.

Twin Atlantic, though, might have hit peak golf. "It's getting a bit much," McTrusty concedes cheerily, "not for me and Barry personally but this is literally the last golf thing we do. We don't want people to forget we're a rock band." Today they're playing a virtual round on the Centenary course at Gleneagles, where the band watched the Ryder Cup last month after playing the opening gala concert at the SSE Hydro in Glasgow. It's unlikely the concert will make their top 10. "It was weird. It wasn't …" McTrusty searches for an appropriately diplomatic summary. "It wasn't the craziest reaction we've had." What was the audience like? "Corporate golf people, who are the worst people in the world," McTrusty says, laughing. "Not all of them but most of them. It was a selfish project because golf is what I do in my spare time. It's like meditation for me. All I can think about for four hours is golf, so I don't worry about reviews or band stuff or the business side of things."

How was the Ryder Cup itself? "Me, Barry and Sam were at the 15th green when the winning shot got hit," says McNae. Did they dress appropriately? "I did because I'm a pure golf poser," says the singer. "I tried to get more 'golf'," says the amply whiskered McNae. "I had trainers and a shirt on." You don't want to stand out in a golf crowd, I suggest. "No, it's not cool," agrees McTrusty, taking a slug from his water bottle.

Peak golf or not, before the quartet get on their tour bus there's a round to get in. Not of beers, but of questions, 18 in all, the aim being to learn how Twin Atlantic found themselves on the precipice of major league success. On the tee, Messrs McTrusty and McNae.

An easy par four to start. Where did it all begin? "We met on the first or second day of school," recalls McTrusty. "Our whole friendship has been around music. Ross's dad plays Scottish folk music on guitar - I'd go over to his house and I'd never seen anyone play guitar up close." He smiles. "We were also listening to the American Pie soundtrack, that pop-punk thing."

Another par four to steady the nerves. How did the now teenage McTrusty and McNae meet the others in the band? When not studying painting at Glasgow School of Art, McTrusty could be found pouring pints in sundry Glasgow watering holes. "I'm a bar whore," admits the frontman. "I worked in Nice And Sleazy, Bloc, the Republic Bier Hall. I met Craig working in Bloc and Barry working in Sleazy's because they were in other bands. The catalyst was meeting them - we formed the band an hour after our first practice together. We were like: 'We've got something here.'"

Time for a par three. What happened next? "We were going to Craig's mum and dad's house and practising from nine or 10 in the morning till five at night," explains McTrusty. "We've been pretty much full time since then. Once we'd started it was all we wanted to do."

A par five now the muscles have warmed up. At this point in the tale Twin Atlantic were building a live audience with UK tours and shows with the likes of Biffy Clyro, Smashing Pumpkins and McTrusty's childhood heroes, Blink-182. How were they funding their musical activities? "We were still working in Nice And Sleazy and B&Q," says the singer. "Eventually we had to make a decision - we couldn't do both," recalls McNae. "We had to not have a job and be poor, but make enough to get to the next place. You were in the van and the only thing you needed was somewhere to stay and food."

Another par five: Twin Atlantic sign to LA label Red Bull Records after Meredith Chinn, a member of its A&R team visiting London, receives a tip-off from a certain Glaswegian music business luminary.

"What's his name?" asks McTrusty.

"Alan McGee," says McNae.

"Why do I always forget his name? He's a pure famous guy. So she asked him, 'Who's worth checking out?' and because we're from Glasgow he said, 'These guys are doing OK.' It so happened that her flight home got delayed and we were playing a show. It was serendipity that she even saw us.

"Our band started at the exact time the music industry collapsed, so we were going into major labels and nobody was willing to take a gamble on a Scottish rock band. We were totally disenchanted. So when we spoke to Red Bull I was like, 'F*** it, we want to be one of the biggest bands in the world, we want to make this our lives.' They were like, 'Give those guys a record deal.'"

A par three. The band records a mini-album, Vivarium. As is common with young bands, asserting their identity fell victim to youthful exuberance. "We wanted it so much that when the opportunity was there we were in a daze for a year," recalls McTrusty. "We sound confused. We sound excited. We were putting five songs into one and trying too hard."

With the turn looming, the first in a trio of par fours. What were they listening to at this juncture? "A lot of complicated rock music," replies the singer. "The Mars Volta, Fall Of Troy … But even the stuff we considered softer sounding rock was still Mew - we thought they were melodic. It was either that or post-rock like Mogwai or Explosions In The Sky."

Gigs. Gigs. And more gigs. "We went to America and did a 50-day tour with 47 shows," says McTrusty incredulously, "and we did a lot of European touring. So many tours in the UK. We wanted to be out working." The graft paid off - once they'd released their first album proper, Free, the band were playing to thousands, not dozens.

Buoyed by their new-found success, Twin Atlantic jettison the ballast of indie credibility and set the controls for the heart of the charts. Says McTrusty, "People ask you: 'If you could write any song, what would it be?' And it's never …"

McNae interjects: "Mogwai's whatever …"

"It's John Lennon's Imagine or Dancing In The Dark by Bruce Springsteen. It's not like all of a sudden we're the big pop machine. We started connecting with people and that gave the band a whole other meaning."

The back nine begins with a par three. How has Twin Atlantic's audience changed? "When we started it was people like us," recalls McNae, "then halfway through Vivarium it was a lot of teenagers."

"Teenage girls, let's be honest," adds his colleague. "Then we started to get radio play and on the last tour for Free it was anybody - couples in their late 50s, 60s, across the board."

A par four called Advice. "I worked with Craig B from Aereogramme in Sleazy's," recalls McTrusty. "A crucial point he said was: 'Don't be f***ing idiots. Take every opportunity you get. My only regret is we held on to our indie morals. All it's done is stopped us and now we have to split the band.'

"We've been at points where our cool-o-meter is telling us: 'Don't do that.' I'm talking about four years after he gave us the advice, and we've said: 'No. Let's stick to what Craig said.'"

A par four: the recipe for success. "We feel lucky," says McTrusty, "but we've made sure we work 10 times harder than anyone else so we're in the position to be lucky. The one thing golf taught me is that if you hit 100 7-irons you're way better than had you not. It taught us the work ethic side of things and patience."

A short par three. Working hard means they now look after themselves, though it wasn't always thus. "For years it was seven men sleeping in a van that sits four people," he says. "We learned how to sneak eight of us into a hotel room."

"Unscrewing windows," sniggers McNae.

"When we look back I'm like: 'How the f*** did we do that?'" says McTrusty. You can get away with murder in your early 20s, I suggest. "And we have," says the singer. "We definitely have."

Another par three. McTrusty is the latest in a growing rank of Scottish singers whose brogue is recognisably Caledonian. Is accent an issue any more? "Some people in America have said: 'I have no idea what you're saying but I feel it,'" says the frontman. "We've had more problems in England over the years," adds McNae.

The last par five of the round and time to address the elephant in the clubhouse: scale. Size. Stadiums. "We're comfortable with the idea of becoming an arena-sized band," says McTrusty. "We don't want the adulation but it's hard to explain the feeling of having all those people connecting to your music."

Great Divide sees the band working with producer Jacknife Lee, whose career was undoubtedly assisted by his work over the years with Snow Patrol, another Glasgow-based group who flew the indie nest (and ultimately Scotland) for more commercial climes. "I always have these sayings," begins McTrusty. "When we recorded Free we were trying to make a timeless rock record. I don't know how many times I said 'timeless'. Then for Great Divide I maybe said the word 'iconic' 5000 times when we were recording."

The final push starts with a par four: the present. All four members have long-term girlfriends and homes in Glasgow, but on the road they have a ready-made tribe in the shape of their crew. "They're like a big touring family," says McTrusty. "Our sound guy did our first-ever gig in King Tut's. He was the in-house guy but we stole him." The singer chuckles. "If we've done 500 gigs he's done 450 of them. It's the same with our guitar techs, and the drum tech is Craig's brother."

Another par four and a slight curveball: much of Great Divide was written in Canada, where McTrusty fled to stay with relatives. "We toured so much with Free that when I came back to Glasgow I was like: 'F***, I don't have anything here.' I've got a bit of family but I was used to being away from them and they were used to me being away. I remember going at 100mph when I came home. It felt like everything was in slow motion so I thought: 'I'm going to try to keep the speed up.' So I ended up writing a lot of the record in Toronto." He pauses. "It isn't as rock-star as it sounds. Like loads of people in Glasgow, I've got family over there."

A simple par three to finish. What wisdom can Twin Atlantic impart to others wanting a slice of the pie? "You have to be best friends," says McNae, quietly. "What touring taught us from an early point is that if you can't let things slide, be friends and get over it then you won't be a band for very long."

Twin Atlantic play Aberdeen Music Hall on Thursday and the Barrowland, Glasgow on Friday and Saturday. Great Divide is out now on Red Bull Records. Visit www.twinatlantic.com.

Thanks to The Golf Lounge, 221 West George Street, Glasgow. Visit www.thegolflounge.co.uk or call 0141 248 1611.