WHEN his good pal Tim Firth took him to see the stage play, The Calendar Girls, Gary Barlow admits that melodies came flooding into his head.

"They just popped out," he said. "I knew then that I couldn't wait to get started on writing a musical."

And write he did. The result of that visit to a theatre in Milton Keynes is The Girls which is currently playing to rave reviews at the Lowry in Salford Quays.

Written by Tim and with songs by Take That star Gary, The Girls is based on the inspirational true story of the women of the Rylstone Women's Institute who produced their own naked calendar to raise money for charity after the husband of one of the members was diagnosed with leukaemia.

"The fact that it is based on such an incredible true story put added pressure on Tim and I to do the whole thing justice," said Gary.

Having already been a hugely successful stage play and major feature film, both Tim and Gary wanted any musical version to be distinctly different.

"Tim had already written an incredibly powerful story without music for the stage," said Gary. "We were never gong to produce a Hollywood-musical style show, the songs are there to complement the storyline and add to the audience's enjoyment and understanding."

For fans of both the stage play and the film, The Girls is a noticeably different production with additional characters and storylines.

It has been several years in the making and Gary has thoroughly enjoyed the whole process.

"I have spent 25 years making pop records," he said, "and The Girls has given me the chance of learning a totally new skill. I fell in love with the whole process - the rehearsals, working with the company, constantly revising and talking about the show.

"I came to appreciate early on that it is not just about what you do, it is about what everyone does. You are very much part of a team."

Gary and Tim have been friends for many years. They first met when they both entered a songwriting competition and discovered they lived near to each other in Cheshire.

"If I want to appear trendy I pretend I grew up in Manchester," laughed Gary

"Tim is a genius," he said. "He really is a master of his craft and I was so happy just to learn from him."

The Girls enjoyed a short run in Leeds before transferring to The Lowry.

"On that opening night neither Tim nor I could enjoy the occasion too much," said Gary. "We were too busy watching the audiences' reaction and analysing everything. It really gets to you.

"You suddenly realise that two acts is a long time in which to tell a story and you want the audience to be involved and make sure that the show flows. You can have a song which you are really happy with but the moment you sit someone in a room and play it to them all you can hear is what is wrong with it"

Perfectionists to the end, Gary and Tim have constantly revised the show - a number of changes were introduced between it closing in Leeds and opening at the Lowry.

"You do become quite obsessive about the whole thing," said Gary. "I've been known to think of something and have to stop the car so that I could phone Tim and discuss an idea with him."

Standing ovations every night indicate that Tim and Gary have hit on a winning formula.

The show has also played a major role in helping raise money for the charity Bloodwise, which carries out research in leukaemia. After every show the cast can be found in the foyer with collecting buckets. In Leeds these collections raised around £1,000 every night.

"The Girls does deal with a very emotional subject," said Gary. "I think everyone has either had someone in their family or knows someone who has had cancer and this makes the whole experience so much more poignant."

Currently The Girls will come to the end of its run at the Lowry at the end of the month. After that, Gary admits, he does not know what will happen next.

"I think everyone involved would love to see the show go into the West End at some point," he said, "but it is not that simple. You need a theatre that is free, putting on a show like this is very expensive, it depends on so many things. We'll just have to wait and see."

But with The Girls clearly having got under his skin, does Gary have plans for more forays in to musicals?

"Whenever I do anything I throw myself into it whole heartedly," he said. "Where Take That is concerned, everything else has to stand to one side. We have a date in Hyde Park in 2016 and will be working on new material. But I have learned so much working with Tim onThe Girls and am really proud of what we have achieved."

The Girls, the Lowry, Salford Quays, until Saturday, January 30. Details from the box office on 0843 208 6000.