Sir Simon Rattle has conducted an unprecedented collaboration of the London Symphony Orchestra and the Berlin Philharmonic, recorded for a multinational first world war event near Mons in Belgium to be attended by David Cameron and members of the royal family.

The commemoration at the St Symphorien military cemetery is one of three big events taking place on 4 August – the centenary of the declaration of war – and the only one with cultural content.

Sir Nicholas Kenyon, managing director of the Barbican and the event's creative consultant, said the theme would be that those who met in war now meet in peace. "The mood of this event is going to be respect for the dead."

The cemetery is a final resting place for soldiers from both sides of the conflict. "Because of this unique situation, with the British and German graves, the natural thing was to try to bring together British and German musicians," said Kenyon.

Rattle chose two works for the LSO and Berlin Phil to record: the last movement of Brahms's German Requiem and George Butterworth's A Shropshire Lad. The latter is laden with symbolism as Butterworth himself died in the trenches. The piece was first conducted in 1913 by the great Hungarian conductor Arthur Nikisch, who led both the LSO and the Berlin Phil in the years leading up to the war.

Because the cemetery is so small, the music has had to be pre-recorded, but there will be a live choir consisting of 30 British and 30 German singers. They will perform a new commission by Howard Goodall accompanied by brass players from both nations.

The other musical highlights will be a solo Bach cello suite, played by the German cellist Jan Vogler, and a song written and performed by a small group of British children who have been working with Gareth Malone. "There won't be a dry eye in the house," said Kenyon.

In addition to the music, there will be poetry and readings, details of which will be announced next week, details of which will be announced next week. Organisers say they are conscious that the event should not portray the war as futile but as a sacrifice for both sides.

The Duke and Duchess of Cambridge, along with Prince Harry, will represent the royal family in the 500-strong audience, while Germany's chief representative will be the president, Joachim Gauck.

The collaboration between two of the world's leading orchestras will be seen as another signal that Rattle is heading to the LSO once his contract with the Berlin Phil ends in 2018.

Kenyon said it had been fascinating to watch players from the two orchestras coming together. "There were interesting little problems, like they don't play at exactly the same pitch. There were little adjustments to be made, but everybody made them and it was perfect."

A former Proms director, Kenyon was asked by the British government to take on the job at the end of last year, but it was a visit to the cemetery that led him to say yes.

"That was the thing that persuaded me to take this on in the first place. I was slightly dubious because I'm not an expert in the first world war," he said. "The cemetery is so evocative and so beautiful it just begs to be brought to life in this cultural way."