private void HideCanvasChildren()
{
keyLine.Visibility = Visibility.Hidden;
for (int i = 0; i < r_instrument.Length; i++) {
r_instrument[i].Visibility = Visibility.Hidden;
r_separators[i].Visibility = Visibility.Hidden;
tb_instrument[i].Visibility = Visibility.Hidden;
}
r_separators[r_separators.Length - 1].Visibility = Visibility.Hidden;
}