Over the last three summers conductor Daniel Barenboim and his West-Eastern Divan Orchestra have been performing all nine Beethoven symphonies across the world. Formed in 1999, this is no ordinary orchestra. Its members include Israelis and Arabs. The idealism of Beethoven's music makes it the perfect choice of repertoire. The three-year tour - called Beethoven for All - finishes this summer at the BBC Proms, in the Royal Albert Hall - the first time in 70 years that all nine symphonies have been played there. Two centuries after they were written, Beethoven's nine symphonies are a landmark in western music. Each sets a new challenge to conductor, orchestra and audience. In the summer of 2011 the orchestra toured China and South Korea - where all nine symphonies were performed together for the first time. The BBC joined the tour to discover why they are regarded as one of the pinnacles of classical music.