If any encounter can be both heart-rending and heart-warming, this is it. On one side of the hall stands a virtuoso musician in the prime of life. Some say he is the world’s finest violinist. Certainly you would have to go a long way to find a human being who so obviously demonstrates such a perfect rapport between mind and body, eyes and brain, brain and fingers, physique and inner emotion. As Maxim Vengerov plays, so his whole torso sinuously sways and arcs in an ardent physical expression of the music that flows from his Stradivarius. This is the package – the handsome, 32-year-old Russian, the mesmerising virtuosity, the priceless piece of old wood – that is said to command fees of £20,000 or more for a night’s work in the world’s top concert halls.

But today Vengerov plays for nothing. Or rather, he plays for love. We are in a magnificent panelled hall at the Royal Hospital for Neuro-disability in Putney, southwest London. Arrayed in front of the musician are about 60 wheelchair-bound patients who, in many cases, have minimal control over their limbs, their minds – and their lives.

Rarely can such contrasting extremes in the human condition have been brought into such charged proximity. Rarely can a man capable of conjuring such transcendental beauty out of thin air have faced an audience that knows such physical deprivation.

“What appeals to an audience like this, what gets through to their subconscious, are two things,” Vengerov tells me later. “Rhythm and serenity.”

He puts that theory into practice now. Standing within touching distance of the front row, he makes a disarmingly simple announcement. “Here are two pieces,” he says. “In the first, my violin sings. In the second, my violin dances.”

That’s all we need to know. The fiddle says the rest. It soars into the luscious melody of the Méditation from Massenet’s opera Thaïs, and suddenly there’s a perceptible frisson in the hall. I look round. Some patients are conducting the music. Some are nodding in time. A few start to hum or gurgle. The Royal Hospital specialises in rehabilitating adults with traumatic brain injuries as well as providing long-term care for people with severe neurological conditions such as multiple sclerosis, cerebral palsy and Huntingdon’s disease. Not everyone here is capable of making a significant muscular response to the music. But nearly everyone – nurses, patients, families and friends (for word of Vengerov’s appearance has got around) – is smiling as he plays. It’s as if a mysterious alchemy has lifted spirits, eased pain, transcended the most desperate circumstances – if only for a while.

The branch of medical science known as music therapy was introduced to Britain from America about 50 years ago, though the power of music and dance to ease mental illness was known to the Ancient Greeks and well appreciated by the time that Robert Burton wrote his classic treatise, The Anatomy of Melancholy, 400 years ago. Music therapists today are highly trained and well regarded in the mental-health field, and much research has been done into how and why musical activities can trigger beneficial responses in seriously ill patients.

Vengerov does not pretend to offer that kind of clinical expertise. Nevertheless, for the past ten years he has been an honorary Unicef ambassador, and in that role he has played to distressed children round the world, and particularly in war-torn Africa and the Balkans. “Music has a far greater potential to heal than we yet understand,” he says. “In fact, it is the only language you can speak to traumatised or brain-damaged people. And they appreciate it. I was in Uganda, playing to children who had been abducted by the army and made to do and watch terrible things. Brutality had destroyed childhood innocence. They were very rough. If you tried to talk to them – no way. But once I started playing, it was an icebreaker. They started to dance, to play their own African music. They saw me as a friend.”

His second piece is the most famous of Brahms’s Hungarian Dances. It’s tricky enough as Brahms wrote it, but just before it finishes Vengerov adds a dazzling cadenza – a cascade of mercurial notes that leap from his fiddle like sparks from a firework. He may be giving a free concert. He may have a bruised arm, the result of slipping in his bath a couple of days earlier. (“It is God’s punishment because I have been unfaithful to my violin,” he says. “I have been playing the viola too much recently.”) But for this audience he’s not going to ease off on his trade-mark showmanship.

“Of course not,” he says. “This kind of work is my first passion. This is where I think music belongs. And it has a wonderful effect on me, too, not just on these people here. You see, when you talk to severely brain-damaged people, they may not understand what you are saying. But once you start playing music, you are speaking to their subconscious. And what happens is that the effect of that bounces back. So I, as a musician, get in touch with my own subconscious. It goes in both directions, this therapy.”

The Royal Hospital organises 50 recreational activities a week for its patients – everything from concerts to gardening, art workshops and theatre (a group of actors was recently resident for several weeks). “Our programme is about improving the quality of our patients’ lives and lifelong learning,” says Claire Stonier, the head of social and recreational services. “And it’s about bringing the outside in for those who can’t easily get out.”

That’s admirable. But it’s not every day that the patients are entertained by a world-class virtuoso. So how did Vengerov get there? The answer, aptly, is that he’s there because of what another legendary violinist did many decades ago. During the Second World War the great Yehudi Menuhin selflessly put himself and his art at the disposal of the war effort – playing a huge number of concerts (sometimes six a day) to Allied troops, and then – after the liberation of the concentration camps – also performing to the benighted survivors of those terrible places. The experience marked him profoundly. Some say that he was never the same violinist afterwards. But for the rest of his long life he devoted himself to countless humanitarian causes.

One of those, which he established with a merchant-banker friend called Ian Stoutzker, was a remarkable charity called Live Music Now (LMN). “Yehudi had this belief that music could help distressed people overcome their sufferings and introduce beauty into their lives again,” Stoutzker says. “So he conceived a project that would give young musicians the chance to earn money at the start of their careers, and at the same time bring music into the lives of the disadvantaged.”

Thirty years on, LMN is a phenomenal (though underappreciated) success story – and it’s to celebrate this anniversary that Vengerov has been persuaded to play in Putney (he also plays at an LMN Gala hosted by the Prince of Wales at Windsor Castle tonight). Musicians are recruited fresh out of college, given training in how to communicate to different audiences, and then sent into hospitals, day-centres, special-needs schools, and even prisons (LMN has recently worked for the first time in young-offender institutions). All styles of music are offered. On a budget of just £1.3 million, 3,000 concerts a year are given to 200,000 people.

Two regular LMN performers, clarinettist Helen Paskins and pianist Ivana Gavric, are playing in the same concert as Vengerov. “There is no training for this sort of work that is as good as actually doing it,” Paskins says. “Autistic children, especially, get very involved with the music. They don’t have any inhibitions. You learn to channel that amazing energy.”

“And as a musician,” Gavric adds, “you learn to programme music with a specific audience in mind, which is something they don’t teach you at music college. You also learn how to communicate. I think both of us would find it very hard to do a normal concert now without talking to the audience.”

Every musician who has worked with the mentally or physically disabled attests to the remarkable effects that music can have. “When Yehudi started Live Music Now he was really just guessing about the power of music,” says Stoutzker, himself a former violinist. “Now the science has caught up. We know for a fact that music can unlock areas of the brain that have seized up. And I have seen the most astonishing things: people who were entirely nonverbal suddenly speaking again. In Scotland once I saw a woman who had been in a wheelchair for five years get up and dance. She had the capacity to move, but never knew she had it.”

Vengerov has had similar experiences. “Once I played in a hospital for children with cerebral palsy in Kosova,” he says. “They warned me that there would probably be no reaction from the children. But there was one girl, miraculously, who started singing when I played. And you know what? Very well in tune!”

Long after the event was due to end, Vengerov stays behind, chatting and launching into impromptu Bach. “This sort of activity runs in my genes,” he says. “When I was a kid in Siberia my mother transformed a school into an orphanage for kids from the street – often children of addicts and alcoholics. On the top floor she set up a music centre and started children of 5 or 6 on music. The transformation in them was wonderful. Unfortunately their older brothers and sisters then came upstairs and destroyed the pianos. My mother was crying. But you know what? She rebuilt that music school, and eventually the older ones started to come into the music classes too. She is my inspiration.”

The extraordinary encounter is over. The wheelchair-bound are pushed back to their wards. The master musician is whisked back into the whirl of international concert life. It’s easy to think that the meeting has been all about a gifted individual bringing joy into tragically disadvantaged lives. But that’s not how Vengerov sees it. “I’m humbled when I meet people who live in the face of such adversity,” he says. “I was very inspired today. For me, these are the greatest concerts.”

For more details of Live Music Now’s work, visit www.livemusicnow.co.uk

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