Gradually, over the course of this simple musical welcome, Caleb, Adrian, Laura and Amy, seem to calm down and focus on her. As Angela moves on to other songs she uses her keyboard, and gets the group of primary year 2 children to choose from her collection of percussion instruments to beat a rhythm.

Making pleasingly contrasting noises with rain stick, stirring bowl, bongos and various kinds of rattling pods, the children set to and improvise, then go back to the familiar songs they associate with Angela.

With the help of simple tunes and Angela's encouragement, plus a little help from a teaching assistant, the children are making music. About 20 minutes is the limit of their concentration, and it has been an intense period in which all of the youngsters have contributed.

After Hello, hello, hello… the three boys in the morning's second group choose to sing Old Macdonald had a farm and Angela tries to get them to focus on making quiet sounds.

The natural inclination among these children with learning disabilities seems to be to beat the living daylights out of the tambourine and drum. Asking for – and getting – a more muted and controlled sound is a tall order.

One of the boys responds by experimenting with taking the sound down a few notches, bashing the bodran a little less frantically. The others are definitely enjoying the more raucous sounds they are making, and are looking not only at Angela, but at those beside them, to see how they make their noises.

As Angela packs up her considerable kit onto a trolley to move to another classroom, she sums up the effects she sees music therapy yielding in special needs children like those at Woodlands School, in Scarborough.

"It's not just half-an-hour of enjoyable music-making," says Angela. "It helps them to understand their own bodies and their relationship with others. It provides non-verbal communication, which is vital to anyone who can't process language properly."

Angela, formerly a viola player with the Hallé Orchestra in Manchester, works not only with special needs children but also with adults who may have suffered brain injury or be profoundly depressed, and with elderly people affected by dementia.

The exact results of music therapy are difficult to quantify because, if it is offered at all in a school, it is part of a multi-disciplinary approach of teaching and therapies. But, from what I'm seeing here today, there is a palpable effect on the children in terms of increased animation and a certain amount of co-operation and confidence.

"I worked with a boy who couldn't speak his first words until he was nine," says Angela.
"I watched his various body movements and wrote a soundtrack to match them.

"After I played the music a few times, he cottoned on to what I was doing, and then changed his movements to see what I would do, waiting to see if I'd change the music. That's very clever; the music was prompting a response that other things did not."

There are some 660 music therapists across the UK, but only 20 in Yorkshire. Angela and three colleagues are based at the North Yorkshire Music Therapy Centre, in Malton. They all have postgraduate qualifications in music therapy, and the profession became state registered 10 years ago.

After marrying a farmer and settling in the area, Angela trained as a therapist in Cambridge, and now works with schools, hospitals and individuals all over the county. The charity's Music, My Voice appeal has raised £150,000 in the last seven years to help local children benefit from music therapy, but fund-raising can be hard going.

Fifty per cent of the sessions run by NYMTC are funded by individual schools or institutions, or by families' contributions. Other funding comes from grants and fund-raising by the team and the charity's supporters. None of the therapists is employed by health or education authorities.

Woodlands is a state school for two-to-16-year-olds with moderate learning difficulties. It's one of 11 schools with which Angela works regularly, and she's been coming here one day a week for seven years.

"Our decision to offer the children music therapy was because it seemed to hold possibilities for engaging children who are very difficult to engage," says acting head teacher Annette Fearn.

"Around 86 per cent of our children have communication difficulties, and 50 per cent are autistic. Music therapy seemed a good route to take in helping children who have significant levels of anxiety and problems with interaction.

"There was some cynicism, but we persuaded the governors by identifying specific areas of need in individual children for Angela to work with.

"After a while, we could see better engagement with learning, reduced anxiety and better behaviour. Later, Angela moved into working with groups as well as individuals.

"Music therapy is, in my opinion, really worthwhile. The children here often have communication problems, but they are highly sensory. It's just a matter of finding out how they will learn, and the music definitely helps.

"We also involved some staff in working with Angela, and they've fed some of what she does into other activities – for example, using a sing-song voice or using certain pieces of music to identify activities, like 'tidying-up music' or 'sitting down music'.

"To many of our children, verbal information comes across as garbled, but music doesn't present the same difficulty as words."

Angela works with 25 of the 90 children at Woodlands across the year, at a cost of £4,000.

Joanna Vanus brings her seven-year-old son, Silas, across from Hackness primary, a "fantastic"mainstream school, to have an individual music session with Angela Harrison once a week at Woodlands. His learning impairment is not severe enough to mean he needs to be schooled here, but Joanna feels the music therapy is a must.

"Once a week he gets to be musical, sharing experience of recorder, keyboard, percussion and strings with Angela. He may never learn to read music – he's having enough difficulty learning to read his own language – but he's clearly interested in it and responds to it, and finds it a joyful experience. He really misses it in the holidays.

"It helps him with number learning, and it has improved his self-esteem, which is so important in a child who doesn't necessarily understand what he should be doing and how to fit in."

Angela's final class of the morning is with six youngsters aged between five and seven "Some of them can't really use speech," says Angela. "One girl doesn't seem to get involved at all in many other activities, yet she will register emotion when hearing music."

The session is clearly hard work, with Angela striving to engage and keep eye contact with the children as she gently prompts a response
to the songs.

Despite concentration difficulties, most of the group seem to grasp the notion of taking turns, and at which point in the music they must bang, beat, shake or rattle their instrument. Their enjoyment is obvious.

"What we do is not about teaching the children to learn music, but about working collectively and using music to help them to communicate. There seems to be a growing awareness of musical involvement in developing other skills like self-determination, control, patience and concentration," says Angela, who recently won an award for outstanding leadership from the Duke of York's Community Initiative award panel.

"And yet, music therapy remains widely misunderstood. People think that we are either teaching music or playing CDs to people to calm them down.

"The active participation is what makes music therapy so powerful, whether we are working with a young man who has come off his motorbike and damaged his brain, a girl with a rare condition which has resulted in paralysis, an older man who has lost his sense of who he is and who he loves through dementia, or a young boy with autism who is too fearful to face the world, to speak or to learn.

"You never know what might happen, and you have to be prepared to go through a range of emotions with the person, from desperate frustration to joyful exhilaration, shared in the music-making."

www.music-therapy.org.uk or tel 01653 698129.