HE’S lauded as one of Scotland’s greatest ever singer songwriters, a pioneer for its cultural identity.

But now Dougie MacLean is adding to his world-famous repertoire of hit singles, movie scores, live music extravaganzas and festivals – by taking perhaps his best-loved work to the stage with “Caledonia – The Musical”.

“It’s a musical – I’m in the middle of working on it,” he smiles. “Caledonia – The Musical. It’s just something that I wanted to do. I’ve been trying to keep it a bit of a secret, but I’ve been enjoying the process of doing it.”

Scots of any vintage will have little trouble knowing the song from which it takes its name. Written in 1977, it was recorded two-years later, and amid a plethora of cover versions, popped up to some fame on the 1991 Tennent’s Lager advert by Frankie Miller, reprised by MacLean himself years later.

But while it might be one of Scotland’s “other” national anthems, it’s clear for MacLean that it means so very much more. “I wrote the script myself, I wrote the story, which is a nice thing to do at my stage of life after all these years as a travelling troubadour and songwriter,” he says. “I’ve got so many songs, there’s 250 songs I’ve written over the years and I’ve got this great story – it’s a love story – and it’s cool.”

He revealed that it was his time spent in Glasgow, as musical director at the Citizen’s Theatre for the hugely successful A Scots Quair trilogy staged by Glasgow’s TAG theatre company in 1993 and featuring Sunset Song, that lay the foundations for his move into musicals.

He said: “I thought to myself, I know how this works, I can visualise a stage production; I’m performing all the time; I know how audiences work, I know the songs that I’ve written over the last 40 years and the ones that work onstage with people, so it’s great to just make a story and bring all those songs into that story.”

While he wants to keep the core theme under wraps – its worth waiting for – he hints: “It’s amazing that a song that I might have written for myself, that if you put it in another situation, it changes the whole dynamic of the song.”

And he hopes it will strike a chord with a new generation of fans, as well as those who love the song and his other bodies of work already.

He said: “Caledonia was a homesick song. I wrote it when I was on a beach in Brittany in France. I finished it and was staying in a youth hostel with three friends who were Irish, we were busking basically in the streets around France.

“We’d jump on a train, see a nice town and get off, did a few wee gigs and I finished the song off.

“I remember going back to the youth hostel where we were staying, singing it to them, we were all that homesick anyway, and we left the next day.

“The first time I ever performed it was in West Berlin. I’d gone back to Germany and was touring around and I didn’t do many of my own songs at that time, I did a lot more traditional songs, a bit of fiddle, and I snuck this song in and the audience just loved it. Even way back then, I was 24 maybe, I turned around and said we’ll keep that in the set.”

And he is proud he did. “Caledonia is only a tiny, little part of what I do. But there’s something about it that became part of common culture which is fascinating and which is a great thrill for a songwriter to have something that is part of it – that is sung at football games, played at Scottish weddings, is played at funerals, you hear buskers singing it in the streets. I have incredible stories about it, you can’t invent that. There’s probably not a night goes by and there’s not a drunk standing somewhere singing Caledonia.”

MacLean will be back at the Glasgow Royal Concert Hall this Sunday, with his traditionally inspired show The Gael, a collaboration involving skilled and talented musicians Ross Ainslie, Finlay MacDonald and Gus Sicard plus other members of the piping supergroup TRYST and select special guests for this year’s Piping Live!

He said: “It was really nice of the guys to ask me to come along and be part of the Piping Live! Festival because I had a long history with bagpipes. When I joined The Tannahill Weavers when I was 20, that’s when that whole piping revolution was happening. I remember when the band Alba told us they were getting their Highland bagpipes out, we were all – you cannae get your Highland bagpipes out in a folk band because they were B flat and what have you. But these guys worked out how to do it.

“The concert is more of a solo concert with me touching my cap to the piping tradition. I’ve always liked to use whistles and bagpipes, rather that saxophones – because they are Scottish.”

MacLean says Scotland is in rude health, culturally, shaking off the stereotypical caricature of the Harry Lauder years, adding: “There’s a lovely, modern, sophisticated image that we have now and I’d like to think I’ve been part of that whole cultural revolution that began to happen around 40 years ago.”

Next month he turns 65, but he laughs: “I’m busier this year than I’ve ever been. I remember a famous American actor said, ‘If you’ve got a job, you retire, if it’s your work – you just keep doing it’. As long as I’ve got a voice and I can drive and travel, I’ll keep on doing it.”

Dougie MacLean performs at the Glasgow Royal Concert Hall this Sunday, 7.30pm, for Piping Live!