Cellist Yo-yo Ma has thrown his support behind Samuel Wong, the embattled musical director of the Hong Kong Philharmonic Orchestra. He said it was a great joy to work with Wong and admired his decision to give up his career as an eye surgeon to devote himself to music. 'It's such a pleasure to work with a musician who has his head and heart and passion for music always in the right place,' he said. Ten musicians have quit mid-contract this year amid what some claim is dissatisfaction with Wong and falling standards - claims the conductor dismisses as 'growth pangs' in an orchestra increasing in stature. Asked about the controversy yesterday, Ma said working in a group was always difficult but he always regarded it as an opportunity. 'The world is not built by pessimists, it's built by optimists, it's built by people who really want to create. 'You cannot make music unless you trust each other . . . You have to be there for each other. It's not about technique it's about where the heart is.' Organisations constantly needed to reinvigorate themselves, he said. 'I think Hong Kong deserves the best orchestra in the world because it's such a fabulous place. But it needs lots of people to constantly invigorate the organisation so that the community can be really proud of what it has made.' Ma was speaking at a press conference dominated by questions from primary school children, including one who professed to be a fan of the cellist because his name was the same as the toy. 'I like the yo-yo. I'm not very good at it,' Ma confessed. He played a short Bach piece using 11-year-old Adrian Chan's half-size cello, and posed for photographs with the children. Music tells stories, Ma told the children: 'If you use your ears, your heads and your hearts, you can go to amazing places . . . that's why I love to play music.' Ma and the Philharmonic will play Haydn's Cello Concerto in C and Tchaikovsky's Rococo Variations in a concert tonight to be broadcast live on TVB Pearl from 8.05pm, and on RTHK Radio 4.