Gustavo Dudamel, sits in front of me, shaking his boyish curls, and laughing. For a man with so much resting on his young shoulders, he is remarkably carefree. The Venezuelan-born newly appointed music director of the Los Angeles Philharmonic is charismatic and sweet-natured. This 28-year-old is a salsa-dancing, movie-mad, prodigiously gifted musician whose two favourite words in English are “delicious” and “beautiful”.

He is viewed by many – including Sir Simon Rattle, Daniel Barenboim and Claudio Abbado, who have all coached Dudamel – as the phenomenon who will attract a new generation of fans to classical music. But he is not concerned only with conquering concert halls, but with changing lives. He believes in music as a force for good, as a factor in turning around lives that are going wrong. It’s a philosophy he has brought from his early days in El Sistema, Venezuela’s radical free music education programme, and one he hopes to apply to other tough parts of the world, including the badlands of Los Angeles. He brings the Simón Bolívar Youth Orchestra from Venezuela to the Southbank Centre in London for a residency next month.

As we talk, in a swanky hotel suite overlooking Central Park, New York, his phone rings. “It’s my grandmother,” he says, smiling and apologising for having to take the call. Engracia de Dudamel is a key person in his life, and, of course, he must speak with her. Until he was 12, the family lived with Dudamel’s paternal grandparents in Barquisimeto, Venezuela. Then his father, Oscar, a professional trombone player who played with salsa bands, took a job in another city. Young Gustavo, an only child, was already enrolled in El Sistema, showing great promise as a violinist. He had also wanted to play the trombone but his arms were too short. So, Dudamel stayed with his grandparents. When a well-known violin teacher in the capital, Caracas, accepted him as a pupil, his grandparents happily got up at 3am each Friday to take him to his lessons. His grandfather died five years ago. In 2005, as a way of saying thank you, he bought his grandmother an apartment.

Dudamel’s parents now work full-time for El Sistema, set up in 1975 by the celebrated economist and conductor José Antonio Abreu. Funded by the Venezuelan Government and other benefactors, it has achieved world renown as a highly effective vehicle for social change. Dudamel describes Abreu – who has become almost a second father to him – as “an angel in the world. We are so proud of him”. Abreu, a diminutive 69-year-old with big glasses and a gigantic heart, saw Dudamel’s potential early. It was when he was watching Abreu conduct a performance of Mahler’s Second Symphony (The Resurrection) that the young violinist decided that he wanted to become a conductor. “It was like, ‘Wow!’ An amazing inspiration. He was conducting from memory and I could really feel the deep love he had for the music. I still have the video of that performance and am very affected by it.”

Dudamel is from a middle-class family, but many of the children in El Sistema come from poverty. Music has been their salvation. “When you are able to focus on music and love to play in an orchestra, you learn so much about community.”

Some 260,000 children in Venezuela have been exposed through El Sistema to music from a very early age and gone on to play in a network of regional youth orchestras. The most outstanding musicians are in the Simón Bolívar Youth Orchestra.

Dudamel has seen first-hand how music can change lives. A good friend, Lenor, who played clarinet in the SBYO, spent time in a detention centre. “Holding a clarinet” Lenor has explained, “was much better than holding a gun.” Having grown up in El Sistema, Dudamel is now the catalyst for bringing it to other countries. He has already started working with underprivileged children in Los Angeles on the YOLA project (Youth Orchestra LA). “We have to build something for the future and involve our young communities, so that they can think as citizens and become part of and involved in society. Of course, it’s wonderful that kids have the internet, television and computer games, but it’s so important, too, that they know about culture and the arts, that they can have pleasure in reading a book, creating memories and talking to friends.

“The young musicians in the orchestra are great musicians but they are also fantastic human beings. They don’t only speak about music, because to be in an orchestra you need many other life skills, including how to lead and how to be part of a team. They care for one other. I joined as a violinist when I was l3 years old. Some of the players were just little kids. It’s amazing; now a few of us are married, but we are still so close.”

Dudamel officially takes up the baton in October with Bienvenido Gustavo, his welcoming concert at the Hollywood Bowl. The inaugural season gala at the Walt Disney Hall includes City Noir, a new LA Philharmonic commission from John Adams. It will be broadcast worldwide – not bad for the boy from Barquisimeto, who was music director of the SBYO at just 18.

Thanks to his recording contract and requests to guest conduct, Dudamel now spends most of his life travelling. But his heart is in Venezuela and his orchestra. “Many in Latin America consider Venezuela to be a Third World country but musically, the Simón Bolívar Youth Orchestra is first world. It’s our soul – our flag – and we are very, very proud of it.”

Not so long ago, Dudamel would have let his wife, Eloisa Maturén – 28, a journalist and former dancer – translate for him. But now his English is fluent and Mrs Dudamel can have some time off. “She’s such a huge support,” he beams. “When we’re travelling she’s always writing, and being a dancer, she is also very musical, so our life together is delicious. I love her so much.”

We meet before Dudamel’s first press conference in Los Angeles. The day after our interview he is conducting, from memory, Mahler’s Fifth Symphony with the New York Philharmonic. With all the praise, you would be forgiven for expecting a young man with a huge ego and an entourage of assistants. What you get is an extremely polite, shiny-eyed, old soul in jeans. Most top conductors are dressed by celebrity designers but not this one. “I buy wonderful tuxedos near Chancery Lane and a lady in Venezuela makes special shirts for me.”

One of the offshoots of El Sistema is a string-making business that is creating jobs. There is also a school where 600 students are learning how to make cellos, brass and woodwind instruments. Duda-mel thinks all this could be replicated.Nearer to home, Sistema Scotland, which was inspired by its Venezuelan forerunner, has been awarded funding from the Scottish Arts Council to establish an orchestra centre, known as the Big Noise, in the deprived Raploch area of Stirling. Other local authorities are taking note. And in two weeks, Dudamel and the SBYO begin their London residency, offering a programme of concerts, open rehearsals, symposia, and a chance to watch Dudamel working with local children.

“I come from a country where everyone has a right to learn music and now I have the best job in the world,” he says.

Is he ever nervous conducting famous orchestras. “Nervous? No. Never. But if you ask, ‘Am I excited?’ Yes, of course. It’s always a delicious opportunity to work with people who have so much experience, to put your ideas across and convince them how you want the music to be. For me that’s the most beautiful challenge.”

I first met Dudamel in 2001 when I was writing about an American youth orchestra from Boston on tour in Venezuela. In Caracas, watching Dudamel work with his musicians, it was clear that he was someone special. Watching the two very different orchestras interact was a vision of how our world could be – in much the same way that Daniel Barenboim’s West-Eastern Divan orchestra, with its young Palestinian and Israeli musicians, gives us hope. Not surprisingly, Dudamel and Barenboim have plans for their orchestras to work together.

“We have to believe in things and work for other people and for the next generations. Those are the only things that truly matter.”

Sounds Venezuela – The Simón Bolívar Youth Orchestra of Venezuela

Residency, Southbank Centre, April 14-18; Dudamel conducts the SBYO on April 14 and 18 (returns only). www.southbankcentre.co.uk, 0871 6632500. The Tour edition of Fiesta, with Gustavo Dudamel and the SBYO is out April 13 (Deutsche Grammophon)