Four years ago only one child on the Raploch estate in Stirling was learning a musical instrument. There are now 450 kids who are not only playing instruments, but are part of an orchestra. And now they are set to take the stage with some of the most famous musicians in the world.

The bell rings for the end of the day and the children from two primary schools stream into the shared area.

But they do not go home. Instead, most have a quick snack before settling down to orchestra practice.

Just a few years ago the people of the Raploch estate, nestled at the bottom of the rock on which Stirling Castle stands, would have found this impossible to imagine.

Raploch, built mainly as a council estate in the years before and after WWII, was not the type of place where people played the cello after school.

The area had a "reputation", and it was more famous for drugs and crime than it was for music.

It was an area of low educational achievement, lack of opportunity and high unemployment.

Brian Conway, who has two children in the Big Noise orchestra, says it would have been beyond his "wildest dreams" when he was growing up to imagine the children, especially boys, carrying violins around the estate.

He says it was a "tougher place" when he was young, with far fewer opportunities for children.

Catherine Jones, who has five children in the orchestra, adds: "There was not much for kids to do.

"There were no youth clubs or things like that to go to and you would just wander, basically.

Image caption The Raploch estate has been undergoing a major regeneration project

"You had nowhere to go, no social space, no nothing. Kids have got a lot more now."

Like many of the parents in Raploch, they are not keen to dwell on the past, instead looking forward to a brighter future for the musical youth of the area.

The first note of musical transformation began when Richard Holloway, the former Episcopal Bishop of Edinburgh and ex-chairman of the Scottish Arts Council, heard about El Sistema in Venezuela and was "converted".

Since 1975, the country's free music education system has trained more than a quarter of a million children from all backgrounds, operating almost 200 children's orchestras.

In 2008, Holloway, a natural evangelist, helped to bring an El Sistema off-shoot to Scotland, which was set up under the Big Noise banner.

He chose to base it on the Raploch estate, home to about 3,000 people, because it was the "geographical and historical heart of Scotland".

Analysis It's almost exactly four years since the Big Noise orchestra played their first public concert. The venue was a marquee behind the school, families turned out in force with toddlers and babies on their shoulders. The musicians weren't much bigger, the oldest just primary three. It had the feel of a school concert - some short, and slightly squeaky numbers delivered with enthusiasm - and then we dispersed. It was the last day of the summer term. But year by year, the true power of Sistema Scotland has become apparent. From Stirling Castle to the Albert Hall (the Stirling version - although it can only be a matter of time before they play the London one) the venues have grown along with their musical skills. Like Venezuela's El Sistema, on which it is modelled, it's as much about confidence and discipline as it is about learning to play a musical instrument. Gone are those first fidgety players, too busy waving at their mums to watch the conductor. In their place, passionate, confident musicians, keenly listen and working as a team. And yet the oldest are still only 11 and 12 years old. Now they are to play with the Simon Bolivar orchestra, the very orchestra which inspired them. As the opening concert of the 2012 Festival, the cultural precursor to the Olympics, it is potentially huge. The excitement is tangible and it's a community-wide effect. Raploch once only made headlines for its crime. Now it makes them for music.

But he also chose the area because it was undergoing a major urban regeneration project. Hundreds of new houses were being built, along with a new community campus for the two primary schools - one Roman Catholic, one non-denominational - and dozens of environmental improvements.

Holloway says: "I've seen it happen in other places where they do a lot of physical regeneration but don't pump enough into what you might call the spiritual regeneration.

"So I went to Stirling Council and said if we find the money would you allow us to do the experiment?

"They bought into the mad experiment and it has worked."

They started as a summer school, with 30 children playing string instruments five mornings a week.

Then six musicians from the Scottish Symphony Orchestra were drafted in to play on street corners and in front rooms across the estate, spreading the word as part of a "cultural bombardment".

It has now built up to a team of 16 musicians working with 450 children - which represents 80% of primary age youngsters on the estate.

The children start in nursery with a cardboard orchestra, where they learn the basic concept of what an instrument is.

They move on to real instruments in primary school.

There is practice after school on three afternoons a week, and they take their instruments home at the weekend.

Ms Jones says it has helped her children with confidence and self-esteem.

Two groups of people of different ages from different continents - many of whom have not had an easy start to life - playing together in perfect harmony

She says her 12-year-old son Neiro has responded well to the discipline involved in being part of the orchestra.

"Neiro has really settled down and is concentrating a lot better. He is here every day and really likes it," she says.

"The girls are more bubbly now. Tieya was really shy and now she's confident and will speak to anyone, and Nyree is focussed on where she could be when she is older if she continues to play music."

Research published by the Scottish government last year concluded that Sistema Scotland had the potential "to achieve social transformation".

Of the parents questioned, all felt their children were more confident, more than 90% felt their children were happier, nearly 80% thought they were more willing to concentrate, and 43% thought they behaved better.

The children play a wide range of instruments, from violins and double bass, to flutes, clarinets and tubas.

Image caption Catherine Jones's five children are in the Big Noise orchestra

Sistema Scotland spokesman George Anderson says: "The orchestra teaches people how to co-operate and get along with each other.

"They are learning something that is hard to do and they get status when they crack it, which gives them such confidence."

The music project has also brought the community together.

Mr Conway, whose children Brandon and Amber Rose play in the orchestra, says there was a "fractious element" between the two schools before they moved on to the new community campus.

"I grew up in this community and to see all the schools coming together with this music is amazing," he says.

"Before the campus you had separate schools, separate endeavours - but now everybody's pulling together. Big Noise is the cherry on the top of the cake. It's fantastic."

Ms Jones says: "The kids are all brought together and they are all communicating together, which is a better idea. Although they've got different religions - now they are all one."

Pauline Kerr, whose seven-year-old daughter Kirsty is in the orchestra, says: "Raploch had a reputation but it is going away.

"There are new people moving into the community and new housing projects. It is getting better.

"The Big Noise is motivating people, and not just children, it is motivating the adults as well."

There is also an adult version of the orchestra called The Noise, which has 45 members.

There isn't a more famous orchestra on earth and there isn't a more famous conductor than Gustavo Dudamel Richard Holloway

Jackie Brander, whose daughters Laura and Jennifer play violin in the Big Noise, has herself taken up the instrument in the adult orchestra.

She says: "The children are better than I am. They like to tell me I'm playing the notes wrong."

Rosie Rice, who works as a support worker at Our Lady's School, plays the cello in the adult orchestra.

She says: "I can't believe what they are teaching us. I love learning a musical instrument. I never had that chance, but it is never too late.

"We are even getting taught how to read music. They are so good with you and so encouraging. When everybody walks through the door we are all at the same level, learning a musical instrument, and we are all having fun doing it."

Ms Rice is also a support worker with the Big Noise, offering a touch of "TLC" to children who are finding the effort a little too much.

She adds: "It's a big commitment for them and sometimes they just want to go home, but I'm so proud of them for all the effort they have all put in."

Image caption Brian Conway's two children are in the Big Noise orchestra

Ten-year-old Taylor Fleming is back in the orchestra after quitting for a short while.

She says: "I wasn't really enjoying it as much. It wasn't as much fun. But now there are more tutors and more people involved and the orchestras are bigger."

This week is the biggest so far for the Big Noise.

On Thursday, the children will take to the stage in front of 8,000 people at a special concert in Raploch which is part of the London 2012 Festival.

The Simon Bolivar Symphony Orchestra of Venezuela, the pinnacle of the El Sistema project, are spending the week on the Scottish estate before the concert - which will see some of the Big Noise performers playing side-by-side with the musical superstars.

Conductor Gustavo Dudamel, whose own musical education began in a Sistema when he was five years old, is patron of Sistema Scotland and has been keeping a keen eye on its progress.

The charismatic 31-year-old says: "Music can change society. It changes family and community because they have access to beauty, to sensibility, to creativity and to discipline. These are elements for a good citizen of the world."

The Raploch scheme was the first Sistema outside Venezuela, but others are joining very quickly.

Image caption The community campus is the heart of the urban regeneration

A number of Scottish local authorities are looking to adopt the scheme, but money and political remain obstacles.

Since it began, Sistema Scotland has raised £3.5m. However, its five-year commitment ends next summer.

Stirling Council will take on more responsibility for funding in its area, but will need a lot more cash to keep the scheme running at the current level.

Nevertheless, the always ebullient Holloway says he expects a "flowering" of Big Noise orchestras across Scotland over the next five years.

He says the presence of the world-famous Simon Bolivar Orchestra on a small Scottish housing estate is "galactic".

"There isn't a more famous orchestra on earth and there isn't a more famous conductor than Gustavo Dudamel," he said.

"They have brought this orchestra to Raploch and the world is going to be looking in.

"If that does not give Scotland a jolt and say 'yes, we must have more of this', then it will take a volcano."

The Big Concert is being broadcast on BBC Four from 21:00 on Thursday 21 June .