I have joined a choir by mistake. This time last year, I was adamant I could not sing. But now, here I am, with 15 other people in the Cafe Oto Experimental choir in London, and we are each singing one long, even note, in whatever pitch comes naturally: this is the composer Pauline Oliveros’s Sonic Meditations.

You are probably imagining a cacophony of bum notes, but it is the opposite. Our voices fall in together in a huge harmonious chorus that fills the space with beautiful sound. As we shake off any lingering self-consciousness, people reach for higher volumes, and the hair on my arms stands on end. My eyes are shut and I feel as if we are floating.

For me, singing like this has become a welcome respite from the noise of the news and other stresses. I am not alone; choirs that require no auditions are on the rise across the UK. Making Music, an organisation that supports a cross section of “leisure-time” music, has seen a rise in registered vocal groups from 1,781 in 2014 to 2,065 today. Rock Choir is a franchised choir that started in 2005, to get people singing rock and pop by removing the usual barriers to entry to amateur choirs, such as knowing how to read music or passing a nerve-racking audition. Its membership has rocketed to about 30,000 people in the UK.

Facebook Twitter Pinterest ‘Lifetime friendships, jobs, housemates … it’s pretty much a lifestyle’ – London City Voices choir. Photograph: Matty Swan Photography

Individual groups also seem to be seeing a rise in numbers. London City Voices has gone from 10 people in 2012 to 450 at each rehearsal. “It has been life-changing for loads of people,” says the choir’s musical director, Richard Swan. “My wife and I met in the choir, as have loads of other couples. Lifetime friendships, jobs, housemates … it’s pretty much a lifestyle. Our semi-jokey hashtag is #notacult.”

Sacred Harp singing is also growing in the UK since its arrival in the 1990s. Groups sit in four blocks facing one another, leaving a hollow square in the middle, where people take turns to lead the singing. While it is rooted in religious singing from New England and the southern US, you are not expected to be a believer. Cork hosts the biggest Sacred Harp convention in Europe, with 200 attendees; last year’s UK convention in Bristol was its biggest yet, with 160 attendees from the UK, Ireland, Germany, Norway and the US.

Co-organiser Steve Brett points out that Sacred Harp groups are not, technically, choirs – there is no conductor or director, and they do not perform or practice. “When we sing, we’re singing to and for each other,” he says. “So it’s a bit different. I think the non-performative aspect attracts some people who wouldn’t otherwise sing.

“All four parts are written to be enjoyable to sing. There are fireworks between the parts, because it’s not designed to be listened to, it’s designed to be sung.”

Facebook Twitter Pinterest The Cafe Oto Experimental choir, with Jennifer Lucy Allan, back row, second from left. Photograph: Alecsandra Raluca Dragoi/The Guardian

Like others I speak to, Brett struggles to put into words the feeling he gets from singing in a large group. “It’s just so powerful,” he says. “It’s not something you get a sense of from listening to a recording. You’re surrounded by loads of people who are also singing in full voice. Singing next to other people like this, you are showing a lot of vulnerability and you tend to form very strong bonds with people very quickly.”

If singing together can feel like exposing ourselves, it also generates feelings of trust and togetherness when we take the risk. This is something that is at the core of the Hope Community Gospel choir in Beeston, Nottinghamshire, run by Barbara and Stephen Thomas. They took over the choir in 2014, when they were volunteered for the task by Stephen’s goddaughter. At that point the choir had dwindled to around a dozen people. Now, there are up to 80 at rehearsals. There are no auditions, and although hardly anyone has musical training, Barbara is adamant: “If you enjoy what you’re doing, you’ll make a good sound.”

The Thomases, who are both social workers, are proud that the choir is a place where anyone, including those with disabilities, can join in. Their youngest member is 23; their oldest is in their 80s. Choir members come from a diverse range of backgrounds, ethnicities and religions. “All of those tensions or divisions that might have been there, between black and white members, atheist and Christian – it doesn’t matter, because we all go through the same struggles in life,” says Stephen. “This is a community choir; you have to embrace everyone.”

Facebook Twitter Pinterest Sacred Harp singers in Bristol. Photograph: Anne Altrinhgam

Some of their members also come for therapeutic reasons. For a while, a woman brought her husband, who had dementia. He would scream at various intervals, but he loved it, and the group were unfazed by his exclamations. They tell me how it was only after the death of a choir member that they discovered she had been walking long distances to attend. “It makes it worthwhile when you’re giving back to people who might not shout about their needs,” says Barbara.

Lucky Kaur runs drop-in sessions and singing groups in St Austell, in Cornwall. Trained in Indian classical and western choral music, she also trained as a psychotherapist and was a social worker, and initially brought the two parts of her life together in vocal workshops she ran at the town’s soup kitchen. She has since taken this practice into other spaces, where it forms part of rehabilitation programmes, and also runs an open drop-in session. “I live near the sea,” she says, “and this singing is about anchoring people.”

At the group she ran at the soup kitchen, she saw that singing was more than just a social activity. “Homeless people often don’t feel they have a voice,” she says. “But when we got everyone in a circle and made sounds, it became polyphonic and harmonious. We practised using our voices – how to project your voice, for example – as in a traditional choir, and I used to keep the front door open, so passersby would hear people singing inside.”

Kaur says that many of us don’t know how to use our voices – whether that is about projecting across a room or just being able to vocalise our needs – and her sessions build confidence and help singers get to know their voices. Singing like this, she claims, can help us feel as if we can speak up in other parts of our lives.

For all of the people running them, a choir is often not just a choir, but also a social club, a community and a charity. For me, it has become a refuge; I can’t check my phone when I am hollering and humming, and holding a note distracts me from the usual clutter of my mind. At the end of a session, as our voices fade to silence and I feel the boards under my feet again, there is a deep silence that descends – a gleeful peace that fizzes like static in the room. I ask Kaur about this feeling – is it just me, or does this happen in other groups she runs? “Oh yes,” she says. “I’ve seen that. I’ve seen tears; I’ve seen big smiles … There is a wonderment on people’s faces. It’s just beautiful. Absolutely exquisite. I think it’s out of this world.”