RICKY Ross has all the look of an expectant father about him; excited, slightly nervous, with a visible wonderment in his eye.

The Deacon Blue frontman’s baby, he reveals, has been gestating for a very lengthy three years. But the waiting means emotions are even more heightened.

“It’s really exciting,” he says. “I can’t believe it’s about to happen.

Ricky’s arrival is due at the end of the month and it’s called The Choir. It’s the story of a community choir, written the musician with Paul Higgins.

Ricky’s move into musical theatre isn’t entirely new; in 1996 he wrote music for On The Line, the Dundee-based project about the Timex Factory, and followed it up with a version of Much Ado About Nothing at the Lyceum.

But this is the first time he’s been involved in a musical theatre project from concept to reality.

“What happened was my wife Lorraine was working with Paul Higgins and we got to talking about working together.

“That was great, but nothing happened for a while. But then Dominic Hill (director) at the Citizens’ managed to get the seed money for the project so we kicked off the conversation again.

“Paul then came up with the single idea ‘Choirs’ and I liked it. The idea was developed, about a community choir coming together, breaking up, the egos, the characters involved, and I felt I could come up with something.”

But how to form it? “The funny thing was I didn’t like the idea of people bursting into song, singing chimney sweeps and all that even though I love musicals such as Guys and Dolls and West Side Story.

“I just didn’t think my music could work in that form. What I wanted was always looking for an idea whereby the music would be so integral, that there would be a reason for bursting into song.

“The musical I felt came closest to what I wanted was Cabaret, in which you had the Kit Kat Club format. And so The Choir offers this perfect backdrop, and the reason why people come together.

“It’s about tastes and egos and people wanting to sing lead parts. It’s the sort of situation you have in am-dram.

“But there’s also a sub plot about non-Scots being in the choir and how they are treated. It also offers the chance to look at Scots from the outside in.”

Ricky Ross’s music has been wondrous over the years, songs such as Dignity and Chocolate Girl are now standards. But could be write choral music?

“While we were developing the show we went along to see a community choral group in the Gorbals, and it was great, full of people there for lots of different reasons.

“But the songs they sang were everything from Cold Play to the Beatles. It was really fun. So pop can work.”

It can in a choir format. But at this point in the conversation Ricky makes a surprise admission.

“I hated choirs when I was at school,” he says, laughing. “That was the last thing I ever wanted to do. Mind you, I didn’t join anything at school, the drama society nothing. I was a terrible teenager.

“My mum however had a choir at church and I’d go listen to that.

“But you change your mind as an adult.”

There’s never been a doubt about Ricky’s love for theatre. “When I once went to the Citz and saw Giles Havergal’s production of The Caucasian Chalk Circle you realise you can combine a story with great harmony singing. What a fantastic noise.

“It made me thinking about writing something so simple, stripped down and with almost a chamber music feel. That’s what I’ve been trying to do with this play.”

It’s been a trying, demanding and fun journey.

“I didn’t really knew what I was doing, Paul hadn’t written a musical before and Dominic Hill hasn’t directed one. But that’s great. We’ve all been learning as we go along. And we’ve all put on shows in different form.”

How do you come up with a devise whereby the choir sings a range of Ricky Ross songs?

“It’s a good point. What happens is the choir members bring along a song, and the leap of imagination the audience take is they accept these songs as being representative of the person who brings it.

“For example, if a sixty year-old woman brings a song, it’s in the style of the era she’d like.

“The songs are quite diverse, but ultimately all you try to do is write the best you can.”

He adds, with a real note of pride in his voice; “There is one gospel choir song in the show that I could really see twelve people sing.”

Was there any arm wrestling going on with Paul over the content and lyrics?

“A little,” he says, grinning. “But I’ve written with lots of people over the years and I’m used to it. And we found a way.”

Given this musical experience, has he considered a musical featuring Deacon Blue songs?

“Yes, it’s been talked about and I’m excited by the idea because there are some great musicals out there such as the Carol King and the Kinks show. And it would be easier to do in that the Deacon Blue songs are already written.

“But it’s about finding the time, you need a lot of concentration and this idea has really taken over and become a priority. However, once the curtain comes down on this, you never know.”

Meantime, the world waits to see how his new baby turns out.

“It’s a fantastic feeling,” he says, smiling. “Three years on it’s all set to happen.”

•The Choir, the Citizens’ Theatre, October 24 to November 14. Ricky Ross's national solo tour runs in November, appearing at Glasgow’s Cottiers Theatre on November 12 and 13.