"You have to really concentrate and look here (at me) to play together. And also, let's be happy, yeah? You look like sad!" World-famous Venezuelan conductor Gustavo Dudamel grins enthusiastically at the orchestra.
The musicians look small, serious and slightly nervous as they try not to be distracted by the army of cameramen and stage crew in fluorescent jackets working around them while they rehearse. Under Gustavo's direction, however, they go back to the top and the confident crash of cymbals soon rings out over melodies from strings and woodwind.
Standing to face the audience, the Scottish primary pupils look quietly delighted at the applause and whistles which greet them in the afternoon sun. The rapturous reception comes from the elite members of the renowned Simon Bolivar Symphony Orchestra of Venezuela (SBSOV), who are fortunate to have Dudamel as their conductor full-time.
It is nothing, however, compared with the standing ovation and cheers which the six- to 13-year-olds from Raploch in Stirling receive the next evening as they open the London 2012 Olympics cultural festival on Midsummer's Day.
No amount of rain can dampen spirits here, as 120 children from this regenerated housing estate play the Rondo from Purcell's Abdelazer to an 8,000-strong international audience and numerous TV crews on a stage built on the vacant site of their former primary schools.
They are the UK's first Big Noise Orchestra, established by music education charity Sistema Scotland. Affiliated to the groundbreaking Venezuelan El Sistema programme, long-credited with transforming entire communities in Venezuela, Big Noise follows the same path to social change, using music to teach children key life skills like discipline. This week's concert, following a four-day residency, is helping to expand the scheme here.
Raploch Primary pupils, sisters Jennifer and Laura Brander, aged 12 and 11, say the best part of being on stage with the conductor and his musicians is just "playing!"
As the SBSOV rehearses before the historic concert, sonorous brass and rich strings attract passers-by who stop to listen as the music drifts across nearby streets. The Venezuelans' remarkable talents also include establishing an instant rapport with the young Scots.
"They know what it's like to be a six-year-old in possession of a tuba," Sistema Scotland spokesman George Anderson says.
Venezuelan trumpet player Arsenio Moreno, now 22, was just seven when he joined El Sistema. He says: "It has been a radical change in my life . I have travelled to many countries and experienced many cultures, and that is not just me - it's all of us."
He describes Big Noise as "absolutely amazing".
Scottish Sistema also runs an adult orchestra with members including Maureen Howie, head of Our Lady's Primary and Castleview Primary (for pupils with special needs). She says: "We are always telling the pupils that we know how hard it is now."
While the pupils' developing technical talents are "amazing", more important is their growing ability to persevere, a key life skill to securing a brighter future.
Later, back at the concert, 30 of the best Scottish musicians join the SBSOV to play Beethoven's Egmont before the Venezuelans' set, mixing classical works with a rousing rendition of Auld Lang Syne, while fireworks light up the darkening skies. The orchestra finishes in typically exuberant style, flinging dozens of their vibrant shirts into the audience.
They have already given every Scottish player a medallion, the trademark "first gig" memento awarded to all El Sistema players. It won't be their last performance, with latest news emerging that Big Noise will be going to Venezuela for a return visit.
IMMERSION IS THE KEY
It was in 1975 that Venezuelan maestro Jose Antonio Abreu launched his now world-famous El Sistema orchestra movement. What started in a garage in Caracus with a handful of children now helps around 500,000 youngsters across the South American country.
Key to its success is the focus on immersion, with children playing together from day one, helping to build both musical and life skills.
Scotland's version, Big Noise, was set up in Raploch in 2008, growing from just 30 string players to 450 children from babies to 13-year-olds.
Around 75 per cent of all primary-aged children in Raploch are now involved, with those aged six and over playing together in a full symphony orchestra.
Now a little frail, Abreu has come to Scotland this week to witness a historic performance of the fledgeling Scottish musicians with elite El Sistema players The Simon Bolivar Symphony Orchestra of Venezuela.
They are led by the SBSOV's musical director, renowned conductor Gustavo Dudamel, who is also patron of Big Noise.
Richard Holloway, chair of the charity Scottish Sistema, which runs Big Noise, is delighted that a reciprocal visit is now planned. Meanwhile, he hopes Abreu's presence and the worldwide focus on Raploch will encourage the Scottish government to fund expansion of the scheme into Glasgow, Aberdeen, Dundee and Fife.
"This week has been volcanic!" he says. "To get these lovely, passionate Venezuelans working with our children here .
"It's wonderful that the founder has come all this way. I think when they (the government ministers) see this, because it's going worldwide - and the impact it has had on this little community, and that the Venezuelans believe in it, they will want to support it."
Last year, the Scottish government published an independent evaluation of the orchestra which concluded that Big Noise was having a "positive" impact on children's personal and social development, increasing confidence and pride while improving social skills, including teamwork.