Often, an enthusiastic response to a performance is nothing remarkable. Here, it certainly was. The audience gushed inside a usually decorous opera house, Gustavo Dudamel crouching to young musicians in "Venezuela" shell suits, sending eyes upwards to the galleries, helping them to take it in, whilst others sent their instruments above their heads in a trademark victory gesture. It's just the sort of passionate reaction you feel "El Sistema" is meant to provoke. The series has hit the ground flying.

Gustavo Dudamel © Richard Reinsdorf
Gustavo Dudamel
© Richard Reinsdorf
The nine concerts of Venzuelan orchestras and choirs have their roots in a similar series at the Salzburg Festival, unravelled three years ago by La Scala's current sovrintendente Alexander Pereira, who was then head of the Festspiele. There is a strong social message – that music has educational value – and it sees the opera house opening its doors with the distribution of 3,000 free concert tickets to Milanese residents. Not without its critics, El Sistema enables disadvantaged Venezuelan children to play in orchestras, its aim to generate broader social change. "700,000 children taking up an instrument," says Pereira of El Sistema. "700,000 children can change an entire country".

Filling the stage tonight, the Orquesta Sinfónica Nacional Infantil de Venezuela made an imposing sight: 400 players aged eight to thirteen, violin desks in six rows, bassists on foot wrapping the outskirts and, if your eye stretches that far, an impressive artillery of percussion at the back. Other elements of the mix include three harps, and at least 25 french horns.

A scratchy rendition of Stravinksy's Scherzo fantastique contained moments of promise. Rimsky-Korsakov described the piece as “fierce, like a toothache” and “agreeable, like cocaine." No such ferocity here, but players found their mojo when amassed strings produced a cozy nuptial flight of the queen bee. Twenty-year-old Sistema product Jesús Parra replaced Riccardo Chailly on the podium, La Scala's Principal Director out of action due to back problems. Slight, fresh-faced Parra could be five years younger. When he stared a player in the eye, extracting his sound from the texture with a clean incision, he bared the sense of purpose of a conductor twice his age.

The subsequent sonic wall turned us to rubble. Gauchos brayed and stomped to driving rhythms. Strings greedily enveloped limping piano in the movement that followed. Parra sliced through a rainforest with tenacious swipes in the third. Ginastera's Estancia depicts an Argentinian cattle ranch in four cast-iron dances. The final Malambo whipped into a lasso whirling party, percussion sticks rising high and projected trumpets beating in time. 

Gustavo Dudamel substituted Parra for Tchaikovsky's Symphony no. 4. A Sistema product himself, Dudamel surely acknowledges that the work is no pushover for a young orchestra: it calls for dark psychological soul-searching and wicked technique. There were odd moments of astringency, with tuning issues blighting the woodwind's second movement weeping willows. This did not detract from a thrilling account, in which detail abounded.  

Trombones found blistering traction when they excavated the opening passage. Bows racketed off strings in the ensuing tempest. Dudamel dug out visceral, nosediving cellos when we stepped out of the eye of the moderato con anima storm, passing the energy around the orchestra with sweeping, flattened palms. Emotional engagement was evident: the face of one particularly miniature bassist provided visual accompaniment in the rolling second movement, frowning and wincing as he eased into his strings.

The start of the third movement is something like a still life of "bubbles in a champagne flute" set to strings – around 200 of them in this case! There was wondrous synchrony between the masses, who leant in unison when the volume nozzle was turned up and down. Dudamel kept out of the fray, steering the wheel whilst the players took care of the propulsion. A glimpse of his face in the final movement belied fierce resolve. His two vertical hammer blows provoked stunned silence, concluding a devastating climb to the pinnacle in which sparks had flown. On a long final chord, Dudamel stretched with open arms, embracing the entire orchestra. 

The applause poured, then roared, long before the final note had ended. In one respect, it was an emotional response to a thrilling musical display. In another, it was a rational appreciation of these young musicians' achievements. Finally, it was an instinctive recognition of what this concert symbolised. Eminent musicians played with high passion and not a hint of pomp. The formalities had fizzled at La Scala's fiesta for all.

Three encores followed, including an extended medley for cuatro duet and The William Tell Overture, directed by another sharp looking El Sistema junior who couldn't have been more than twelve. Here was a sprightly conductor. The legacy is in safe hands.