I FEEL utterly exhilarated. I am breathless and can still feel the adrenalin pulsating through my veins. Endorphins are popping away in my head, making me feel on top of the world. I can see my friends smiling and applauding. It is one of the best moments of my life.

This, reader, is what being in a choir can do to you. Even a non-audition community choir filled with singers that struggle with timing and can’t always hold the notes. The sort of choir – in my case St John of Jerusalem community choir in Hackney, east London, in 2011 – that would have Johan Sebastian Bach turning in his grave if he could hear our rendition of his Magnificat.

You’re not thinking of Bach, however, when you’re singing his 300-year-old masterpiece. You’re far too busy following the notes on the page to the best of your ability, trying to keep your section together, digging deep within yourself to create texture, emotion and harmony in the singing. It’s bloody hard. But it’s also the most joyous thing you can imagine. Put simply, it makes you feel fantastic.

Of course, there’s a fair chance that you or someone you know is a member of a choir and already familiar with this feeling. Choirs – a bit like baking – are nothing short of a phenomenon these days. There are groups of all sorts, from gospel to pop, rock to classical, and many that mix all these genres and more, springing up in church halls, community centres and workplaces across the country. Some make you audition, many don’t.

Anybody can have a go at singing their heart out. And since there is estimated and 25,000 choirs in the UK – including at least 50 in Glasgow at my last count – it’s clear that many of us, particularly women, are doing just that.

Mass singing isn't new – we used to do it all the time in churches and round pianos in parlours. But the decline of the church and the replacement of the family sing song with radio and television left us rather unused to it.

Gareth Malone gasps when I tell him about the 25,000 figure. He seems genuinely surprised. “Really? I can only apologise,” he laughs.

The baby-faced, bespectacled choirmaster is the man whose TV shows The Choir, Sing While You Work and The Naked Choir have done more than anything else to get us singing – he is the Mary Berry of singing, a middle-class icon. Speaking to me from his home in London, Malone is just about to go into rehearsals with his own choir, Voices, in preparation for their UK tour in the lead up to Christmas.

His voice sounds a bit weak and husky, partly due to a nasty cold he’s been nursing for a couple of weeks, partly because he’s tired after a weekend celebrating his 40th birthday (can he really be 40?). Malone comes across similarly in person to his TV persona – confident, articulate and informal with a good line in camp asides.

Viewers have been watching Malone put singers of all abilities through their paces for nigh on a decade, but as part of this live show, which comes to Edinburgh’s Usher Hall on December 19, he’ll be doing some singing himself, performing a song he’s written especially for the tour and a Beatles medley to “please my dad”.

Malone loves coming to Scotland, a place of happy childhood holidays with his mother and father, the latter of whom is originally from the east end of Glasgow. Scottish music and culture, he says, are “part of my DNA”.

“I remember having to translate Rab C Nesbitt to my friends,” he jokes. “Because my dad is from Glasgow I could understand it perfectly well.

“We would spend lovely holidays in Scotland, visiting relatives in East Kilbride and going to Loch Lomond – I remember being very disappointed that I didn’t see Nessie. And then being very upset when I found out I was at the wrong loch altogether.”

The tour is clearly a big deal for Malone. The 15-voice choir comprises a lively bunch of hand-picked professional singers, who will perform his arrangements of an eclectic repertoire of songs by the likes of James Blake, Ed Sheeran and Carly Simon. He says there will be plenty for the audience – many of whom are likely to be in choirs themselves – to sing along with, that it will be a fun, entertaining and cosy show, “like I’ve just invited you round to my front room”.

But as someone who is used to having his back to the audience as a conductor, will he enjoy singing in public?

“I am pretty nervous, especially since I’ve got practically no voice at the moment,” Malone admits. “But I think since I keep getting other people to sing, it’s nice for the audience to see me doing a bit of singing myself. No-one expects me to be Pavarotti, but I really hope they will enjoy it.”

He says the bit of his job he enjoys most is bringing live performance to people, an experience he describes as “joyous”. There’s that word again.

Joy, says Malone, is a big part of the reason why so many people join choirs. They may have watched and loved his TV shows, or films like Glee and Pitch Perfect, which have undoubtedly added to the appeal. But it still takes guts for someone who has never sung in public before to get off the sofa, find a local choir, turn up at rehearsals week in, week out, and perform in front of an audience – as I know myself.

So why do people do it? Malone believes modern life, with its focus on individualism and personal technology, makes us for yearn something more.

“It’s about being with other people and singing together,” he says. “Having said that, there is something just so fantastic about performing as well – the energy and excitement that is created when the lights go down. That’s a really important part of human life.

“But I think choirs have helped us rediscover the simple joy of going out. We’ve all got the most ridiculous set-ups at home that I couldn’t have imagined 20 years ago, where we can watch any movie we want to watch at the drop of hat, play any computer game, listen to any music.

“But actually, what I really want to do is just go out and be with other people and see and feel something that’s live.”

It’s hard to imagine the TV schedules without Malone and his obscenely uplifting musical mentoring. In 2011, his Military Wives choir achieved the coveted Christmas number one spot, beating off Simon Cowell’s X-Factor winner, while a celebrity choir he mentored for Children In Need also made it to number one. He has won two Baftas and been awarded an OBE for services to music and has become that very British of phenomenons: a national treasure.

But such mainstream success wasn’t always on the cards for this only child from Bournemouth, who was mercilessly bullied at school for being gay (he wasn’t) because he liked classical music and sung in the choir.

Being different, Malone says, made him an outsider and thus a target for the bullies. He was strong enough not to follow the crowd, he says. But it was a painful time and he is critical of how his school handled the situation.

“I went to a boys’ grammar school and they didn’t do much about it at the time,” he explains. “No-one seemed to ask us – is anyone being bullied, is anyone having a hard time? It seemed to be a case of 'why didn’t you say something earlier?' but that can be very hard when you’re young.

“My wife is a teacher and from what she tells me things are different these days. There will always be people who pick on others and there will always be people who are on the fringes, who are different. But I just think they handle it better now.”

Malone later formed various rock bands at school, and went on to study drama at university in Norwich, intending to become an actor. It wasn’t until he won a place to study voice at the Royal Academy of Music in London that he found his calling, however, later working with the youth and community choirs of the London Symphony Orchestra, before getting his TV break in 2006.

On his website, Malone, who has two young children, describes himself as a “choral animateur, singer and presenter”. But what does the “animateur” bit really mean? What is he listening for when he meets a group of singers? How do you actually go about making them better?

“In some ways I’m looking for what’s wrong with what I’m hearing,” he says. “Essentially I have a vision of perfection in my head that nothing ever quite gets to. There is a checklist too – is the blend perfect, is everyone singing with heart and character, is the repertoire right?

“As you get further up the professional scale, those things come together more and more. But with amateurs there’s always an element missing and it’s a question of thinking – in the time that I have, what can I most readily effect?”

But what makes someone a good choirmaster? And how does it work on a television show filmed over many weeks with multiple choirs of varying abilities in different locations around the country?

“Sometimes I don’t see the choirs very often – it’s very different to when I’m working with my own group, who are very able and want to be given difficult, challenging things,” he says.

“Sometimes with choirs you’re just setting the bar higher and having ambition for them. With that comes an element of discipline, or making them work harder.

“Obviously you need to be musical, you need to have skills at your disposal and a sense of how you are going to shake things up and make them work. You need compassion too – your singers are going out there to do battle for you and you’ve got to be able to put them in a place where they’re ready to do it. There’s a strong element of psychology to that. I spend a lot of time with groups helping them have the confidence to go out and do it.”

He admits he gets different types of pleasure from working with different types of choirs.

“With inexperienced singers I love the immediate joy of them, and the satisfaction of seeing people discover something new,” he smiles. “With experienced singers, it’s being able to realise my vision for them.”

While watching Malone’s shows, I always wonder how much time he actually spends with the choirs, and whether TV trickery accentuates his role in the process.

But according to Choral Stimulation, the Glasgow-based a cappella (unaccompanied) group that made it to the final of Malone’s latest TV series, The Naked Choir, this is not the case.

Malone’s magic, they say, comes in his ability to make choirs think differently about their sound.

He made regular visits to Scotland throughout the series to work with the group, particularly towards the end of the series, as the final performance loomed. Over five weeks, the group, all students of Glasgow University, wowed viewers with their versions of songs such as Sinead O’ Connor’s Nothing Compares 2 U, Reach, by S Club Seven and Jess Glynne’s Hold My Hand. The group says honesty is key to Malone’s style.

“We couldn’t get away with anything with Gareth,” says alto Hannah Merriman. “Any slight wrong note or pronunciation and he would hear it.

“He was particularly helpful with our tuning and blending and a huge influence to us in terms of our arrangements and performance choices.

“Gareth taught us the importance of stripping our arrangements back so that they are not too busy for the listener.”

The group adds that the national treasure was “pretty direct” when it came to telling them what wasn’t working, but that it brought the best out in their sound and performance.

Choral Stimulation were eventual runners up in the series.

Not surprisingly, Malone is full of praise for the Glasgow choir, and seems genuinely touched when I tell him how complimentary they were about his methods.

After the tour, Malone will make another series of The Choir, then he’s not sure where singing will take him next. It will almost certainly involve live performance.

“For me the most fun in the world is on stage – that is where I am absolutely happiest and most joyful,” he says.

There’s that word again. I think back to my own live choir performances a few years ago. On some sort of level, I can relate, as can the 10s of thousands of people across the country who will sing with their choirs this Christmas. In terms of joy, we have a lot to thank Gareth Malone for.

Gareth Malone and his choir Voices play the Usher Hall in Edinburgh on December 19. Tickets from £27.50 www.usherhall.co.uk or Tel: 0131 228 1155