It's a Tuesday night in Glasgow at the tail end of summer and the Ace chorus is into its second week of rehearsals.

Most of the singers are here in the cavernous church hall a good 20 minutes before the start time, keen as mustard. As they file in - most arrive on their own - they are greeted by Rona McKenzie at the door.

Rona and musical director Richard Johnston set up the choir 15 years ago and put on an annual concert at the Clyde Auditorium. "We had been involved with amateur theatre in Fife, between the two of us, for a disgraceful 60 years," explains Rona.

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The idea was to give people at amateur level the chance to sing show tunes from the big productions. "You come out of the theatre and you've heard these big songs and you think 'How can we sing them?' So we dreamt up this idea of doing a large-scale concert. We've evolved over the years. We still do big show songs but also favourites from Dean Martin and Frank Sinatra plus one or two up-to-the-minute hits."

With time of the essence, vocal coach Claire Christie takes the floor and gets everyone on their feet for some energetic vocal warm-up exercises - then it's straight into the numbers.

Claire is a formidable force but also full of fun. "Can you smile when you sing? No, it's a genuine question. Can you?" Cue nervous laughter.

If a phrase is not spot on, it is repeated and repeated while singers frantically mark counts on their music in pencil.

As the practice moves on, she talks about muscle memory. "Don't save your good singing for the night itself. The more you sing really well, the more you can."

Singing is innate in humans. Babies and young children are incredibly responsive to it, but it is one of life's pleasures which many of us suppress once we hit those self-consciousness teenage years. While we can enjoy a lifelong love of listening to music, for some, the thought of actually singing in public is akin to root canal. But in recent years there has been a resurgence in choir participation, with hundreds springing up across the land.

Many who are joining choirs in recent years have never sang before. The last time Gillian Hoffmann, a community mental health nurse from Kilwinning, did any singing was at school. She is still finding her feet. "During the break in the first week I got chatting to a woman in the ladies. She kept referring to "sops" and I didn't know what that was. She meant sopranos," says Gillian, 40, who sings alto. "I'm still learning the lingo. It's hard work but I expected that. I'm really enjoying it."

Another new start is Linda Gardiner, 61, from Burnside, who also sings alto. After recently retiring as a geography teacher she decided to join with her sister. "I hadn't been in a choir for years and this appealed because I didn't want to do amateur dramatics. I've got a vaguely musical background - I can read music and play piano - but I wouldn't have gone to a choir that you had to audition for."

Linda wasn't quite sure what to expect. "I was quite blown away by the singing in the first week. Obviously a lot of people can read the music or have perhaps sung the songs before but immediately the sound was really good."

Each year the choir accepts a maximum of 150 singers split between the main Glasgow group and a smaller choir of around 30 which rehearses in Fife.

"With so many people, you don't immediately feel part of the big group but they are not unfriendly and everybody is so busy all the time," says Linda.

This year there are 20 male singers including Alex Lawrie, a financial adviser from Paisley, who sings baritone. Alex has sung in several choirs and met his wife Shona when they sang together in an amateur opera group in Glasgow many years ago. The couple joined Ace together this year.

"Previously I did opera or religious choral music and this is more popular music. I suppose there was an element of it maybe being easier for me, but I was more interested in the style of music and getting the chance to sing well and sing out," says Alex, 52.

"My first impression was that it was very friendly. Quite often you find in choirs that when you join it takes a while to get involved with other people, but they were quite forthcoming and made a point of coming up and speaking to me so I felt at ease from the very beginning.

"I do enjoy it. It takes me away from other things. When you are singing you can't really think about anything else, you've got to think about what you are doing and the music that is in front of you so it's a good escape."

The youngest choir member is 18 and there are several ladies in their eighties, but the majority are aged between 40 and 60. Year after year, Rona sees people blossoming in confidence during the experience. "You can come in on your own into a choir and everybody is going to be doing the same thing, so right away you are one of the members and people chat in the break and get to know each other.

"It's a confidence booster. The fact that it is a big group means you can disappear. You're only one of a large number but you are doing the same thing as everyone else and it's giving you confidence because you've got all these people with you."

In common with many choirs, Rona has noticed an increase in interest in recent years, particularly this year. "This summer some of our people have been involved in the Commonwealth Games opening and closing ceremonies and they were phoning up asking for places for people they met while doing that who had never been in a choir but wanted to carry on singing."

Making Music, an organisation that supports community singing groups, has seen a boom in new choirs in the last five years. Today it has 1758 member choirs across the UK compared to 1571 in 2009.

Executive director Barbara Eifler credits a number of factors. "There's the Gareth Malone effect, as we call it. And that's about showing that everybody can sing and can make a beautiful noise if properly led. That has clearly encouraged more people to join or start choirs.

"But people are also more aware of what they can get out of it - that's the second Gareth Malone effect: we have seen how the choir has helped the Military Wives, or the Fishermen's Wives, we have seen how workplace teams have gelled over singing, how much members of choirs are visibly enjoying themselves when competing on Songs of Praise and elsewhere."

The Military Wives choir was launched on the BBC programme The Choir which featured conductor Malone. The resulting single, Wherever You Are, was the 2011 Christmas number one.

"Then, of course, there are initiatives like the Big Big Sing which really captured people's imagination. Suddenly people realise how easy it is to have a go. All these factors together have created a climate where more people believe that making music could be for them."

In recent years, new research has emerged showing the health benefits of singing in terms of both psychological and physical health. A study from the University of Stockholm earlier this year showed that singing increases the levels of oxytocin, the bonding hormone, in both men and women.

Singing is also known to boost immunity levels. Research at Frankfurt University's Music Department back in 2002 compared saliva samples and noted a secretion of antibodies after taking part in singing. Interestingly, the same study confirmed that the immunity boost was not observed after just listening to music: active participation was the key.

Closer to home Professor Raymond MacDonald, head of the Reid School of Music at Edinburgh University, has been studying the positive effects of singing. "There has been a huge explosion of interest around the beneficial effects of community singing.

"First of all music is an excellent vehicle to bring people together and form a group because people inherently enjoy singing, particularly songs that they know and many of these community groups do not require previous experience.

"Community singing gives them a chance to explore their creativity and to develop confidence they may lack when it comes to music because when they come to these choirs they realise very quickly that we are all musical.

"That realisation can really be a huge motivator.

He adds: "When they are sharing these artistic, enjoyable experiences as a group, you get this enhancement in general wellbeing, communication skills, confidence, self-esteem and a reduction in social isolation. People can get together, sing songs, enjoy themselves and form new relationships. All these variables contribute to enhanced psychological wellbeing."

Professor MacDonald believes that music has certain unique qualities which make participating in a music group even more beneficial than other clubs such as book clubs or sporting teams. "There is now convincing evidence from a whole range of sciences showing to what extent music is part of our humanity and therefore universal.

"You can be distracted when you are performing music as well, so if there is something you don't want to think about, it engages our brain."

He refers to research done by American music therapist Michael Thaut who says that when the brain is engaged with music it is changed. There is also research which shows that singing improves lung function and a pilot is soon to be launched in Glasgow to help sufferers of cystic fibrosis.

"Music is physical as well so when you are singing, it's a whole body activity. So all these features come together to make music a unique type of social activity that has considerable health benefits for us particularly when it happens in the right social situation." He cautions against over-simplifying the connection. "Just having the choir itself isn't going to produce health benefits, it's the way in which the choir is run, the way in which people communicate during the sessions and the wider social context. All these features are important."

Professor MacDonald has also been working with patients with Alzheimer's disease at Glasgow's Gartnavel hospital and found group percussion and singing activity slowed their deterioration. "There is a growing body of work showing the positive effects of music for patients with Alzheimer's. Music has a very powerful effect on us physiologically and I think that is one of the reasons we can harness this powerful effect and use it for health benefits."

It's two months on and at Ace chorus rehearsal, thoughts are turning to the concert in ten days time. As members file into the hall from the darkness outside, there is a palpable excitement. The newbies are being issued with their concert attire (red blouses for the women and red ties for the men) and everyone is learning how to get into position on stage. When the singing gets underway, the big sound brings a tingle to the spine.

"I'm looking forward to the concert because of the venue," says Alex. "It's a big space and a 40-piece orchestra will be playing with us so that makes it quite exciting. The only thing I would say I'm a little concerned about is that I'm not allowed to have any music in front of me. I've never been in that position before so I have to learn everything by heart. That's a challenge."

Looking back on the whole experience, he admits the rehearsals were harder than he'd expected given his previous experience. "I am used to rehearsing hard, although maybe not as much in one night. It was fairly intense from beginning to end. The vocal coach makes it fun though and everybody gets stuck in and that makes it good."

The social side has been a bonus. "I've even been out for a night out with some of the male section of the choir, something I've never done with a choir before, so there is a fairly good social thing going on in the background as well."

Linda and Gillian stop to chat to various people. There is a real camaraderie now between members. "I'm more excited than nervous about the concert," says Linda. " I think there will be enough numbers and my sister Eunice and I are tall so we'll be at the back. I wouldn't like to do a solo and I would hate to be in the front row but I think I'll be OK."

She is definitely coming back next year she says. "I have been recommending it to all my friends. It's been a great experience." n

Ace Chorus 2014 Concert, 7.30pm, Saturday November 15, Clyde Auditorium. Tickets from www.ticketsoup.com; 0844 395 4000. For local singing groups visit www.makingmusic.org.uk