In a small, sweltering room, decorated with children's pictures, letters, and moral messages in English and Hindi, Scotland's leading violinist does not need to warm up, but she does anyway, as if she was about to perform before thousands in a concert hall.

With four students from the Royal Conservatoire of Scotland, Nicola Benedetti runs through a vigorous musical workout.

Elsewhere in this school in the heart of Mumbai, 50 neatly dressed four to six-year-olds file into a tiny classroom, waiting for the renowned musician. Ten minutes later, the children sit neatly in seven or eight rows in the stifling heat of the Pali Chimbai Municipal School, run by the Aseema charity, which has nearly 600 pupils in the Bandra area of this chaotic city. The children, all from disadvantaged backgrounds, wait patiently under the fierce eyes of several female teachers.

Loading article content

Benedetti, wearing jeans, a T-shirt and flat shoes, is introduced along with the four students - Alice Aiken on cello and violinists Sam Watkin, Wen Nang and Gongbo Jiang - to the well turned-out pupils.

"Listen to these people who are very, very good at playing their instruments," the teacher explains in English and then again in one of India's many native tongues.

Four short pieces later, the formerly quiet and orderly children are clapping and smiling. The singing strings of Benedetti's warm violin seems to fill the room. The rapt children want "one more!" and ask questions afterwards. One says: "What is that paper?" pointing at the scores. Another wants to know what the bow is. This kind of session - playing to children who may have never seen a violin, or heard western orchestral music before - is at the heart of the BBC Scottish Symphony Orchestra's (SSO) visit to India.

Mumbai is the last stop of a 12-day tour that has taken in Chennai and Delhi. The ranks of the SSO have been joined by 13 students from the RCS, by Benedetti as the featured soloist, and by conductor and composer James MacMillan. There have been three large concerts for adults in each city, finishing with the National Centre for Performing Arts in Mumbai but it is the children that each musician talks about. The director of the BBC SSO, Gavin Reid, says they are at the core of the logistical feat of moving 100 musicians around this vast country.

Benedetti, hours before this session, sipping coffee in a Mumbai hotel, says India has been a life-changing experience. The people, she says, have been "genuinely spiritual in a tangible way. It is a very powerful place".

"It's been absolutely unbelievable. I've fallen in love with this place. I've never been to India before but have known quite a bit about Indian classical music, and I have some friends from here. But it has surpassed everything."

And the children? "They are just as kids are everywhere. Of course there are enormous cultural differences, but if you treat people like people, and children like children, they react to things the same way. You try to find that connection. They were just wonderful and cute and lovely."

In this tour, the SSO - backed financially and in kind by the BBC (Radio 3 are here too) plus the financial and in-kind support of the British Council - have played to thousands of children. At this school Zahira Sheikh, their teacher, says: "These children are from disadvantaged backgrounds, so it is a big thing for them - they have probably never seen music like this on the TV, they will not have seen it in person. When we told them, they were so exited. There is no doubt it is a big moment for them. They'll go home and talk about it and tell their families and friends. The fact a young person could play an instrument like that - that idea is amazing to them."

Music can be a form of communication when writing is not - three-quarters of Mumbai's school-going children from its slums cannot read. Andreia Nunes, another teacher, adds: "The music has such an effect. It can soothe and calm them down. The days we have music here, the attendance is full."

Reid, the avuncular director of the bbc SSO, and a former professional trumpeter, who worked for three-and-a-half years to arrange the tour, adds: "I would estimate that we will have played to 10,000 children, and they have responded brilliantly.

"One of our players, after the schools concert in Chennai, where we played to 1500 children twice in one day, said it was like looking into a nest of chicks because they were so responsive. The response has been beautiful. There have been three highlights for me: the first workshop day in Chennai, when we saw the response of the children to the orchestra, then today in Mumbai with the children here - what I saw today is why I get up in the morning.

"Then in Delhi, when we, unannounced, played to the audience an Indian tune arranged for orchestra - and they just loved it."

Mumbai, this sprawling city of more than 20 million, envelops the senses. The city seems oceanic in scale, in its shifting moods, its potential danger, its noise and occasional beauty. Then there is the noise: the constant horns from the cars, buses, black and yellow taxis and tuk-tuks (auto rickshaws) on the madly jumbled roads. Bollywood music spills from radios and shop fronts, from shacks and mobile phones. There are the smells: fresh fruit, meat and fish for sale, open or blocked drains, cooking fumes, herbs, perfumes and spices and other, less unidentifiable scents.

And there are the sights: multi-storey hotels and business towers, high-rise housing in various states of dilapidation, the hard-packed squalor of the sense-defying slums, beautiful old buildings cheek-by-jowl with precarious, intensely inhabited piles of stone, brick and blue plastic tarpaulin on the brink of collapse. Amid the surging scrum of humanity there are tall green trees, palms and flowers, gardens and stretches of idyllic beach. As you walk or drive, you see glimpses of utter misery: dead animals, black and bloated, tiny slips of children playing in brown-water drains, while mothers beg, hands out, with sleeping babies in their laps. Outside a beautiful, eerily glimmering Jain Temple encrusted with plaster elephants, a hobbling shadow of a man with an arm at the wrong angle begs for rupees, his fingers hanging limp like leaves.

James MacMillan has conducted on this tour, marking a burgeoning relationship with the BBC SSO. He recalls the moment the bus entered Chennai, formerly known as Madras.

"Gradually a silence descended as we began to see the mass of people, the poverty. It was chaos - we couldn't decided whether some of the buildings were coming up or down. There was rubble all over the place, and beggars. You see things that stop you in your tracks. People with no legs, people with profound disabilities looking hungry - it is a shock."

One scene in Mumbai, as a member of the tour haggled with a stall holder, encapsulated the kaleidoscope of colour and emotion. Within a hundred yards, my eye moved from right to left: a group of young boys, well dressed, played cricket with a tennis ball up against a red brick wall. Next to them, a man dressed in neat white linen sold magazines and fruit from a stall. To his left, the huge Gothic red brick bulk of the Victoria railway station, one of the British Empire's legacies, and, in a road tunnel, a black cow dozed in the cool of the shade.

Then, on the other side of the tunnel, four wretched, fish-eyed drug addicts injected heroin into their bandaged legs. One by one they slumped to the pavement. Next to them, four policemen in neat pale uniforms laughed and joked as they drank hot sweet drinks bought from a chai-wallah and completely ignored the prone humanity behind them.

"The difficulty is seeing the level of poverty," says Benedetti, who is 27 years old. "I was in an official car, with two other people. We stopped at a red light for what felt like half an hour - it was probably only three minutes - and there was a woman with her baby, rapping on the window.

"I was having an argument with the two men with me: 'Can I open the window? Let me give her something.' And they said: 'Absolutely not. That is not what is done, it is not legal and it only encourages them.'"

She sighs. "How do you rationalise what the right thing to do is? And be at peace with the level of fortune that you have compared to that? It's impossible. I think the worst thing is to be OK with that - but can you do anything about it? No, not really."

MacMillan says the best thing a visitor can do is support the charities and other bodies trying to make a difference. Benedetti adds: "You can try to be the best person you can be - the most honest, the most truthful person. I cannot affect change to those people. There are a couple of societal things that are hard to swallow and hard to understand. But my general sense is overwhelmingly positive. It's one of the most liberating experiences I've had. I love it. I think I'm going to cry the day I leave. I'm pretty sure I will."

Why take a western orchestra to India? The country has its own deeply revered classical tradition, and extraordinarily diverse and vibrant music. Although there are orchestras in Mumbai and Kolkata, and institutions that teach western music like the KM Music Conservatory in Chennai, founded by the Oscar-winning Indian composer AR Rahman (best known in the west for his music for Slumdog Millionaire), or the Mehli Mehta Music Foundation in Mumbai, there is no national western classical conservatoire. It seems interest in the western canon is resolutely a middle-class interest. A version of Venezuela and Scotland's El Sistema, which works with disadvantaged children and fosters passion for the music from the ground up, would seem to be needed for western classical music to grow deeper roots.

Reid, who played in Mumbai in 1989 with the European Community Youth Orchestra with Ravi Shankar, says: "We are not the first orchestra to come to India but I knew that where there is interest in western classical music, it is really strong. The ambition of this tour is unprecedented. There is growing interest and I get the sense that there is an opportunity to share our music. Why now? The context is the Commonwealth Games, and this seemed to be the perfect opportunity."

MacMillan notes: "Orchestral culture is moving outside its European and American contexts, and India wants to be part of that. We've seen thousands of children and they are thirsty for engagement. It is a little bit of outreach, evangelising, if you like. You cannot get results overnight. You can't get instant results - you have to let things evolve."

Seeds are being sown. John Wallace, director of the RCS, says the institution will work with the KM Conservatory to "grow for the future". Rahman's conservatory has a strings programme and an opera course, and is looking to expand woodwind and brass, and the BBC SSO has a "burgeoning relationship with them". There is talk of RCS graduates going to India to help teach, and Indian students are already at the RCS.

Reid says he hopes the tour has left a footprint and the BBC SSO can return. The concert at the Siri Fort Auditorium in Delhi was televised by Doordarshan, the national broadcaster, and live on All India Radio, which has a reach of more than 700m people. BBC Radio 3 also broadcast the final concert from Mumbai. Professor Fali Pavri, of the RCS, who is from Mumbai, says: "The children have responded with joy and wonder and that will serve them for a long time. You can see that has moved then. But we all recognise the need for teachers and we are doing the best to change that, we have been speaking to every music organisation in every city."

Benedetti, for whom this week in India is just part of a hectic year of touring and production, is clear-eyed on the issue. "India has its own popular music and its own classical music. We are not bringing something that they need. We are bringing them something else that is great - to approach it any other way is patronising and ridiculous. But the reactions have been wonderful, they are such sophisticated people and listeners and they are so open.

"I find it humbling and reassuring. Sometimes you can get into a state where you think the world is focused on the thing you do, but it's not. There's a lot of other things going on. It's good perspective." For her, the core of the tour has been the workshops, masterclasses and school visits. That is what has made the BBC SSO's tour unlike any other.

"It's targeting a variety of goals: to strengthen relationships, to bring western classical music to people here, trying to work in the cities - we are not just arriving in a concert hall and a hotel and leaving again, which is the nature of so many tours and I find incredibly sad, because what are you leaving behind? There is no human integration, no human connection; it is just the music performance."

But, she adds, smiling: "Why do orchestras tour at all? That's a big question - we just like to share something that is good." n