VH's NZ teacher got on to the thumb thing with him, which is definitely helping - I think the root of the problem is teachers who only LISTEN to how things sound instead of checking to SEE how they are being played. Until VH moved to his full-size violin, his giant hands and long fingers meant that he could stretch to high positions without moving his thumb round. He still can...*almost*...just enough of a strain to create a hesitation or a minute variation in pitch.
Makes me cross to think that he asked his teacher several times why he was suddenly having trouble with high positions with his new violin, and she just kept saying everything was fine, just fine...
We're waiting on a couple of introductions - one to a very solid classical teacher, the other to a guy who likes to arrange and play unusual music, but who believes that the further out on the limb you go, the more solid your technique has to be. It will be interesting to see how that goes...
VH's NZ teacher recommended he go back to Wohlfahrt Book 2 for work on positions and do some detailed work on the intermediate-level Mollenhauer piece "Fantasia: The Boy Paganini" (how's that for a title guaranteed to rivet an 11 year old's attention?!)...she says he probably passed his Grade 5 last year on musicality rather than technique, and that she doesn't think he is truly secure at the intermediate level in terms of technique - more like approaching Grade 5 level.
Back in Japan, his teacher is wafting him nebulously through Kreutzer etudes and starting him on Beethoven's Romance #2 for violin and piano. I would be happy for him to do easier stuff and get his technique rock solid while he's still young! (And I admit that I'm a bit more open about it than I would be if his J teacher read English!).
I was amazed at how much detail his NZ teacher went into in discussing everything with him...but VH lapped it up. I think J teachers generally do concentrate on form rather than content (not only in music, there's a general feeling that form comes first, and with correct form comes increased understanding, whereas in the west especially in modern times, we tend to assume the opposite). If children won't do what they're told without asking questions, teachers tend to go to one of two extremes - either become very dictatorial and punitive, or just let the kid do anything at all, on the assumption that they're not serious about music.
