Chang was born in Philadelphia, of Korean parents. Her father, Dr Min Soo Chang, who lends a discreet ear to our conversation, is himself a good enough violinist to have studied at the Juilliard School of Music in New York under Ivan Galamian, one of the century's outstanding teachers; her mother is another Dr Chang. Although Sarah's years on the circuit must have inured her to interviews, she laughs with such frequency that it's plain she still enjoys them - and she's ready for the inevitable questions about her age. "I'm just about legal! People are amazed when they realise that I'm still only 18, because I've been on the concert scene for more than a decade. I started playing when I was four, but I only really started playing and travelling when I hit eight."
Fourteen years with a fiddle in her hand, when other kids were out playing ball, falling out of trees or off horses - doesn't she resent the sacrifice of her childhood? Another laugh. "They always ask that! Actually, we did a very good job in limiting how many engagements I did - not only my parents, but also my management, who were very considerate." She says "we" a lot: this is obviously a team effort.
"So when I went to elementary school and then on to junior high [in Philadelphia], we limited concerts so that I could go to school," she continues. "When I hit high school, of course, I did a bit more. It became more difficult, and I had to keep in touch through faxes and e-mails. I couldn't just go out for these three-week tours and then come back and catch up like that; it didn't work any more. The only reason it worked out is because my school was so amazingly flexible."
The school - "regular private school", she explains, not a specialist institution - appears to have been part of the plan to give her childhood a semblance of normality. "I went to Juilliard on Saturdays, which is something that a lot of kids do. At high school I had to do all the curricular things that are required of you, so I did English literature and science and mathematics. I only just graduated last May from high school, so it's all very new for me."
Has her diary started to fill up now that she can enjoy the freedom of adulthood - until, at least, she decides which university she wants to attend? "Actually, it started filling up when I hit my sophomore year - that's 15 or 16. Now, of course, it's full swing, plus recording projects. So it's something that I wanted, especially this year, because I'm really going to look forward to going to a concert and coming back and being able to relax without having homework hanging over my head. People tease me about that because I always had to rush off after dinner, and they'd think, `Oh, are you going out with friends after this?', when in fact I had to go back to my room and finish my homework and e-mail it before it's morning back there. It was fun, but it was difficult in a way."
Another difficulty must be coming to terms with one's own immediate past: laying down recordings at such an early age means taking a snapshot of an interpretation that is evolving at an exponential rate - when you listen to it in two years' time... "you'll cringe, yes. You do that all the time. I've had some time to get used to the idea that it's never going to be perfect, because I started recording with EMI when I was nine, so that's a massive amount of growth right there. And when I listen to stuff I did when I was nine, obviously I'm going to cringe in some places and wish that I could go back into the studio and do a few notes over again. But at the time, when it was released, I certainly thought it was good enough.
"No, that only shows that you grow. That's like the Tchaikovsky and the Mendelssohn - I'm no doubt going to record them again when I'm 40 or 50, and I'm sure it will be drastically different then. You have to argue whether it will be better or not; it will be different.
"And there's so much repertoire out there for the violin," she adds. "We have our pick. The most important thing for me right now is to look at new composers and newer works."
I am glad to hear this: far too many musicians are content to whizz round the world giving clockwork readings of the same handful of concertos. I have brought some ideas to see how open-mindedly she would react: a recording of the concerto by the unknown Norwegian Catharinus Elling, a gem of a piece that belongs alongside the Bruch and the Glazunov in the standard repertoire, and a typescript catalogue of the works of Julius Rontgen, whose huge Brahmsian output lies in unexplored manuscripts in a museum in The Hague, five works for violin and orchestra among them. Her reaction is heartening: "Exactly - that stuff: we need to do it. Everybody groans that classical music is dying and we're hearing the same things for the thousandth time. We should do something. Would you like a cookie?"
Tomorrow evening's concerto lies close to Chang's heart; indeed, it's already three years since she has already recorded it, with Mariss Jansons and the Berlin Philharmonic (EMI 7243 5 56418 2 3), in a reading of startling maturity - there's a calmness in her playing that you might more readily expect from a much older person. She has, of course, thought about it a lot.
"I adore the Sibelius; it's always been one of my favourites. When I made that recording, it was after wailing that I wanted to do the Sibelius for about five years. We waited until we found the perfect orchestra with the perfect conductor - I was very happy with that combination. And to top it off, when we had the idea for this project - with the Mendelssohn and the Sibelius - they asked which one I would want to do live, because I had concerts in Berlin.
"The Sibelius gets a certain energy and a drive if you have an audience in front of you that you just can't get in a studio. I insisted on doing the Sibelius live, and I think, among the records that I've done, the cringe factor is the least with that one. That piece has got the perfect mixture of iciness and warmth in the old Romantic style. I learned it when I was eight, and in that time-span your love for a concerto usually fluctuates - you love it, you hate it, and you decide to love it again - but with this it was always constant."
Sarah Chang will perform the Sibelius Violin Concerto at the Royal Albert Hall, London, tomorrow, a Prom which will be broadcast live on Radio 3 and BBC2 at 7.30pm and repeated on Radio 3 on 18 Aug at 2pmReuse content