I am in a room with five adolescent boys who are making a right old racket on an array of drums, xylophones, maracas and castanets. They are an eclectic bunch: there is the shy one, the fidget, the brain box, the cool dude and the class clown. And yet when the fidgety one makes a joke about the cakes laid out ready for break time ("Let's start on them now!"), there are good-natured chuckles all round. There is a closeness between the boys because they all have one thing in common.

Winston's Wish, a charity for bereaved children based in Cheltenham, launched an initiative in December last year to help boys aged 11 to 13 to deal, through music, with the death of a parent. "It's about taking the pressure off being too verbal about their loss," says Brett Riches, a musician and youth worker who runs the group. "They might want to use music instead when they're feeling sad or need a boost."

The boys' fearlessly honest articulation of the bewildering experience they are living through is impressive and moving. "It feels as if you're taken to the edge ...and you can't hold it in," says Ben, 12. "It's like you're a train on a winding track," adds Reese, 11.

As they speak, Riches, 29, turns their words into lyrics then, guitar in hand, and with the boys playing percussion, he helps them to work out a melody. The atmosphere of defiant strength but deep vulnerability is enhanced by a poignant chart on the wall. On it, the boys have written why they are here. "Dad, Peter. Heart disease, nobody knew about it. He had a heart attack. 2012." "Mum, Alison. Died of cancer. Late May 2010." "Mum, Carrie. Died 2011. Breast cancer. She died at home." Observing the sixth of eight music therapy sessions, it is clear the boys have made good progress. A group for girls begins this week.

"Kids are often more honest about their feelings than adults," says psychotherapist Philippa Perry. "The important thing with childhood bereavement is that they can be in a sharing situation with people not embarrassed by grief and not paralysed by what to say."

Most psychologists will tell you that there is no standard method for dealing with bereavement, but psychoanalyst Anouchka Grose says that helping children to think healthily about death is crucial: "As an adult, you can learn something from each loss and carry that on to the next one. But death for a child is like an incredible fantasy space. For kids to be able to conceptualise it in any way is amazing."

Gaby Eirew, a Vancouver-based counsellor, believes that technology can help the grieving process. She created RecordMeNow.org for parents to make video memoirs about themselves for their children. "When a parent dies," she says, "children are often left with little emotionally."

Eirew spent five years interviewing 100 people between the ages of 21 and 86 who had lost one or both of their parents before they were 16, and asking them what they wished their parents had said to them before they died. She came across a lot of "weird guilt from people who hadn't been taught to grieve properly". At one point, she was phoned by someone who sounded about six, but who was actually a 30-year-old woman. "She'd got stuck when her mother died when she was six. She was praying for an hour every day because nobody had taught her how to grieve."

Darian Leader, the author of The New Black: Mourning, Melancholia and Depression, believes that adults are "just as bewildered by death as children". This, he says, is why: "Every evening people turn on the TV to watch shows that begin with a dead body and end with a revelation of how the person died." Bereavement is complex today, he says, because of "the erosion of public mourning rituals since the first world war". He adds: "Mourning was initially defined as a public duty, but it's become an individual work of grief, where you have to do the work yourself."

Back in Cheltenham, the music group is in full swing. "Sick!" Ben exclaims when they listen back to the recording of the final song, which is both catchy and heart-wrenching. It has a chorus of "hold on to your memories and don't let go," courtesy of Ben, and a passionately cathartic percussion climax.

All of the boys are excited about their achievement, even Liam. The oldest of the boys at 13, his father died of a brain haemorrhage two years ago. He hasn't appeared to participate much, although Riches praises him for occasionally rapping a drumstick against a small drum. He shrugs: "I'm just going with my beat."

And so he is, like a backbeat in a jazz tune – slightly out of synch with the rest of the band, but just as crucial. At the end of the session, he grins: "See you all next week."

• Some names have been changed

For more information visit: winstonswish.org.uk

• This article was amended on 27 March 2013. The original said that Gaby Eirew interviewed 1,000 people for her app RecordMeNow.org, when she actually spoke to 100.