I don't know about this, it seems like most child stars burn out these days. When I was her age, I wanted to be a professional pianist too, and while everyone including many professional pianists and teachers told me I could, I found that after a while, I think I just lost interest as a function of being a kid. While I continued to play, I only recently re-discovered my goal of being a professional pianist a few years ago, and in some ways I'm grateful. I'm grateful I had a real child-hood, and in some ways, I think I know more about music, I feel that if one spends too much time performing then one has no time for study, especially as a child. Although I'm playing catch-up in terms of repertoire, and maybe in technique, I find that with good and thoughtful practice habits I can appear to stand on even ground with people who four years ago had ten times the repertoire I did. I've found that by out-thinking my peers in terms of both musicality and technique, I can stand above them who have been playing the standard concert pianist repertory since a very young age. In fact, most of the pianists here seem to think I'm better than them, and I'm content to let them believe that.
I couldn't resist the plug for myself at the end of that paragraph there, but what I suppose I'm saying is that I had to experience life before I could decide that it was worth it to sacrifice almost everything for my instrument. And in someways, I think it's impossible for a child to make that decision. I would support her decision, and be just as supportive if she decides that's not where she wants to go. She may come back just as I did, and I think that if her love of music was that great in the first place, it'll survive any changes of heart she might have along the way. I guess I think that you should put more thought to helping her develop more as a person and as a musician than as a pianist, as tempting as it is to use young talent to show case your teaching ability, I don't think it really serves any purpose. To me, a young person speaking with simple music rather than typing liszt etudes, speaks volumes more about the teacher.
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