When Southern rockers Blackberry Smoke wanted a special guest singer for their new album, they went about it directly.

Singer Charlie Starr simply picked up the phone and called Gregg Allman of the Allman Brothers, and put the question to him.

“It was just a case of asking him outright to play,” laughs Charlie.

“We’ve become friendly with Gregg over the years and supported them in the past. When we recorded the song Free On The Wing we thought ‘how great would it be if Gregg sang on this?” It was all about working up the courage to ask him, because he could have said no.

“But he asked to hear it first, and after he heard it he went ‘yeah, I’ll do it’. He could have crushed our feelings by saying he didn’t like it, but every time I hear the song and he starts to sing then I get goosebumps, because Gregg Allman is on our record and that’s fantastic.”

It is easy to understand the kinship Gregg Allman might feel towards the band. Now on their fifth album, the five-piece have kept the torch for old school rock music burning brightly. Their tunes are often rough and ready, drawing on classic rock, pop and soul to blend up a potent brew.

Although their Southern roots are clear, the group have hit it big internationally, with their biggest Scottish gig to date booked in for Monday at the Barrowland.

Charlie has a theory why their music crosses international barriers so well.

“I think it’s because it’s the working man’s music,” he says.

“It’s not terribly angry, it’s feel good music and makes me want to dance. That’s all you want sometimes from a rock n’roll band – make me dance! The last several shows we have done in Scotland have been wild. They’re really rowdy, and great and loud.”

There’s another Scottish connection there too.

“We’re big Frankie Miller fans,” adds Charlie.

“He’s not well known in the USA, but I have a friend from England who now lives in Atlanta. We were listening to records in his house, and I went ‘who is that?’ He said it was Frankie Miller, and gave me all of his records. What a voice.”

The band’s newest record, Like An Arrow, features not just that Gregg Allman appearance but some of the band’s heaviest ever material mixed in with slow-burning blues and country songs.

Produced by the group themselves, the long-haired lads rattled through the recording process, and Charlie was pleased to display some variety.

“If you want to feel good about your integrity and what you accomplish, then do what feels right, and if doesn’t feel right then don’t do it,” he says.

“We have a fanbase that will follow us down whatever rabbit hole we go down, and we have some fans who won’t, who want every record to sound like Little Piece of Dixie or the Whippoorwill.

“I’ve tried to make It clear in interviews that we want to explore things, because the only band that can make the same record over and over again are AC/DC. That’s not to say we will make a hip hop record but we want to toy with the sonic landscape.

“That makes some people uncomfortable and they’ll be vocal on social media – ‘this isn’t like the last one’ in which case oh well. Maybe you’re in for the long haul and maybe you’re not.”

Charlie believes the band’s slow but steady route to success is one reason they’ll be in for that long haul.

“One thing that is very important is that we haven’t had a huge windfall of popularity, so we have never had to answer to a label,” he says.

“We have always enjoyed creative control. Somebody that is young and a pop star might not enjoy that. They’ll be told you sold 10 million copies of your first record so you have to repeat that, and that will affect the songwriting, the live show and everything else, whereas for us the grassroots approach has worked.”

That grassroots style meant they easily adjusted to producing their own work. There was never any danger of spending hours on overdubs or lots of extra instruments.

“One thing we have learned from each producer is not making it too polished,” says Charlie.

“When we worked with Brendan O’Brien, he was all about the performance, and not trying to beat something to death to achieve perfection. Perfection doesn’t sound better than passion.”

Blackberry Smoke, Barrowland, Monday, £20, 7pm

JONATHAN GEDDES