How do you build an orchestra for London?

April 1970: in a school hall in the Liverpool suburb of Mossley Hill, an orchestra is gathering. Some of the musicians are schoolchildren, some teachers. Some are parents and local amateurs. Among them, for guidance and moral support, sit five players from the Royal Liverpool Philharmonic Orchestra. ‘We thought he had a small concert in mind’ declares an astonished organiser to the local press. But there, standing before a 72-piece orchestra with a confidence that startles his elders, is the conductor who’s brought them together – a 15-year old percussionist from the Merseyside Youth Orchestra called Simon Rattle.

February 2015: 102 young musicians in spearmint-coloured T-shirts sit waiting on the platform of the Barbican’s concert hall. It’s been a day of schedules, sectional rehearsals, sandwich lunches and tightly-timed breaks. Instruments are gripped more firmly, the laughter has an anxious edge. And now he’s here - now it’s all finally about to come together.

Sir Simon Rattle’s hair is whiter than in his Liverpool College days, but the smile is the same. Young voices cheer and feet stamp as he makes his way through the violins. ‘Well, how fantastic is this, to see you all here?’ The smile again, and he lifts his baton, ‘Shall we just play?’

So, to work. Repertoire was chosen – Sibelius’ Finlandia and Malcolm Arnold’s Little Suite No.2 – rooms were booked in the Southbank Centre, Guildhall School of Music and Drama, and Barbican, and schedules were drawn up. Players from the London Symphony Orchestra (LSO), London Philharmonic (LPO), and Berliner Philharmoniker were enlisted as coaches, and the animateur Rachel Leach was brought in to help it all hang together – and to guide the members into the worlds of three composers, two arts centres and three great orchestras. Two young British conductors – Ben Gernon and Duncan Ward – split the preliminary rehearsals between them.

A grey Sunday morning in January 2014, and the foyer of the Guildhall School is jammed with instrument cases, coats and music bags. The players have just filed back from a Skype conversation with members of the Berliner Philharmoniker; now they’re seated in a rehearsal hall as Rachel Leach energetically deconstructs, then reconstructs, the music of Sibelius. Without their instruments, the players are divided into three: and there are sheepish giggles as she gets them to improvise a DIY version of Sibelius’s Fifth with clapping, singing and (for a super-keen few) maracas. This afternoon, there’ll be sectional rehearsals. A huddle of LPO players has already gathered in the foyer, clutching takeaway coffees as they discuss what needs to be covered.

So Rattle lifts his baton. The opening brass chords of Finlandia snarl out; the tempo increases as the music surges forwards into the Allegro. He stops. ‘I’m one coffee faster than you are. Don’t panic, let’s just all breathe together’. Again, he raises the baton: suddenly the music is moving faster, and something new is happening. ‘There was a nervous energy that they hadn’t really exhibited yet’ says Ruth, who’s been marshalling the orchestra backstage at the Barbican Hall all day. ‘I didn’t know how that moment would go either.’

But now that moment is here. Players’ eyes lock on; a cellist starts to sway with his instrument; on the back desk of violins, two girls dart wide-eyed glances at each other, smiling in their excitement. The sound grows richer, the ensemble tighter. Nerves start to turn into music, and Rattle begins to push his orchestra. ‘If you knock your desk partner over, it’s not a catastrophe’ The laughter is less anxious, more exuberant. ‘Make a mistake, yes, but make it a really fabulous mistake’. But mistakes, by now, have never seemed less relevant.

The rehearsal runs its course; the performance, too. Little brothers and sisters in the audience lean forward, legs dangling and mouths wide-open – loudly whispering questions mid-Finlandia. No-one shushes them. At last the applause fades, the Young Orchestra for London leaves the Barbican stage.

‘He just seemed like a normal guy!’ explains one player to his parents. A trombonist, beaming, talks into his mobile phone: ‘I’m just chilling out for a bit, trying to calm myself down’. There’s more to come: the Southbank Centre, Zero at the Bone, and the Malcolm Arnold. No need quite yet for new friends to exchange mobile numbers and arrange chamber music dates, or for aspiring 15-year old conductors to maybe start planning their own orchestras.

The Berliner Philharmoniker is on in 25 minutes, and the audience is already studded with spearmint-green T-shirts. Young musicians from every borough in London will be listening as insiders - as colleagues of these German musicians, just as from now on they’ll hear concerts by the LSO and the LPO with an understanding beyond anything that seemed possible seven weeks ago. At the Barbican and Southbank Centre, orchestral music has become for them a shared experience – a process of communication, exploration, aspiration and friendship.

‘Music is like a virus’ said Sir Simon Rattle, immediately before he performed for the first time with these 102 youngsters: now an Orchestra that really does sound, look and feel like London. ‘And what we hope is that everyone catches it and it’s completely incurable. What I hope is that this will grow and grow and grow. This is just the start.’

Find out about more opportunities to get involved with Barbican Guildhall Creative Learning.