You would never find Stoller House by accident. You have to go looking for it.

It’s at the end of a long lane past the Rheged Discovery Centre, just off the Penrith to Keswick stretch of the A66, and it isn’t signposted.

It’s a low-lying, one storey building specially designed to fit into its sloping site.

But you can’t failed to be impressed by it.

It’s one of those places that looks brand new and yet has a very traditional feel to it, as if it could date back centuries.

It’s made from Cumbrian slate, oak and larch and is carbon-neutral, with solar panels, underfloor heating and insulation from Herdwick sheep’s wool.

It is lit by huge windows providing views over fields towards the Ullswater valley - dazzlingly bright on a cold but very sunny day. Plenty of sunbeams are shining through.

And when Annie Mawson plays a gentle Irish melody on her harp, it seems to fit perfectly with that relaxed, serene atmosphere.

Stoller House is the home of Sunbeams Music Trust, the charity set up by Annie 26 years ago to use the therapeutic power of music to help people with disabilities or dementia.

It includes a performance hall, music therapy rooms, meeting rooms and a recording studio, and was officially opened by Sophie, Countess of Wessex, earlier this month.

It’s not always calm and serene, however. From a large auditorium at one end of the building a lot of enthusiastic singing can be heard, accompanied by piano, guitar and drums.

It’s all quite rock ‘n’ roll. They’re singing I Saw Her Standing There , Johnny B Goode , All Shook Up , Loch Lomond and Hit The Road Jack . “It’s not just Daisy, Daisy !” Annie points out.

What’s clear is that the singers, all adults with learning disabilities, get a huge amount out of it. Even those who were shy when they first came are exuberant and enjoying themselves.

People who can be excluded, marginalised or discriminated against, with little to look forward to, come there and feel a real buzz, a real improvement in their quality of life.

Music has always been part of Annie’s own life - but using it as therapy came later.

She only admits to being “over 27”, grew up on a farm near Cleator Moor, and relates: “l have always sung, from when I was an infant, and I began the organ when I was seven.” Even then she was called upon to play at church services.

Annie studied geography at Newcastle University, started playing the guitar as well and joined a folk group. There was a lively folk scene in the north-east at the time and she adds: “They now do a degree in folk music at Newcastle. I would have given anything to do that. I knew I had music in my bones.”

But geography gave her a job - teaching the subject and becoming head of department at Windermere St Anne’s School. She was still making music there and she recalls: “One of the teachers said: ‘Annie, I think you would like working with children with special needs.’”

He was recommending a post at Roundhills School in Kendal, and she ended up staying from 1977 until it closed in 1992, working as a music specialist.

On her first day there she met a young man with learning disabilities who asked her: “Do you want to see my Bible?”

He took from his pocket the complete works of Gilbert and Sullivan, and Annie says: “He knew every single opera. We used to sing Gilbert and Sullivan songs when we were gardening.”

It was then that she discovered how music could work wonders with disabled people.

“I met children there who were elective mutes- who could speak but chose not to. Yet they sang beautifully.

“Or there were elderly people with dementia who don’t know their own names - but knew all the rock ‘n’ roll and skiffle from their youth, and would be up rocking and rolling and jiving.

“You could have children with hearing impairments who love to lie on the floor just to feel the vibrations of the harp.”

And whoever they were, whatever their age or the nature of their disability, music seemed to bring them great joy.

Annie doesn’t make claims for music over other forms of disabled therapy, such as art or exercise. They can just as effective, she insists.

But she does say: “I see daily proof of the transformative power of music.”

Why does it work so well? It’s known that newborn babies will sometimes seem to recognise music they heard while still in the womb - responding to the themes from TV programmes, for example.

“Hearing is the first sense we have,” Annie explains. “Five and a half months into pregnancy the acoustic nerve is fully developed.”

And when Roundhills School closed the absence of music therapy was noticed.

“Parents were ringing me saying: ‘Our children aren’t getting any music. Nobody understands how important it is to them.’”

Cumbria County Council bosses at the time didn’t understand how important it was either. Annie stresses that they're much more enlightened now - and very supportive of Sunbeams. But back then they sounded downright hostile.

The Roundhills staff were being interviewed for new jobs within the county’s schools and she was upset and angry by what one interviewer said.

“I was told: ‘If you continue your pursuit of music therapy you’ll never be employed by us again.’

“I walked out of there thinking: ‘I’ll show them.’”

So there and then she decided she’d go on providing music therapy - and one day open a purpose-built music centre. Sunbeams Music Trust was founded.

The first donation came from Annie’s then eight-year-old niece Rebecca, who gave her the £13.60 she had saved up.

Now, 26 years and £2.7 million later, the centre is a reality - and Rebecca is one of its trustees.

At first Annie was offering music therapy in people’s homes or in residential homes.

It grew steadily, and to help fund the work she became a professional singer and harpist in 1994. Performances have taken her far beyond the north of England - to New York, London, Belfast and at one point many venues in Essex. “I was in danger of becoming an Essex girl!” she recalls.

Her work with disabled people was recognised with the title “Woman of the Year” in 2000 and an MBE in 2014.

A specialist centre was always the aim andr Norman Stoller’s Stoller Charitable Trust provided £1 million of the £2.7 million total. The building is named Stoller House in recognition of that.

It now allows Annie and her team of professional musician to lay on workshops several times a week and provide music therapy to more than 1,500 clients every year. Another 1,600 are on the waiting list.

Fundraising is an ongoing job, with £300,000 needed every year to fund the work. But there are moments every day, she says, that make it worthwhile.

“When you are reaching a child with profound disabilities, and they respond to something they’ve heard, it's very special.

“We help to change the public perception of people with disabilities and we just try to brighten their lives for as long as we can.

“Every session there’s something wonderful happening.”