Some of the simplest tasks are the most effective. The 3rd movement opening of Moonlight sonata, a student plays each 4-note 16th group with the standard “arm out to the side” movement to shape the group. But this pulls her thumb off the board so it’s not ready to play the first note of the next group. Then the arm movement she does make to play the next thumb note is so big that her thumb feels no need to work on its own, and becomes inert.
I kill two birds with one stone by having her play the first five notes very quickly and overhold the last two. try that now: play G#-C#-E-G#-C# and hold on to your fifth finger G# while standing firmly on your thumb C#. The two outside digits of your hand make pylons that stand your hand right up like a bridge. The movement was so quick that your arm had no time to do its normal garbage but went straight to the goal. It moved your thumb in towards the backboard instead of pulling it away. And the arrival on the thumb’s C# was so sudden that it galvanizes your thumb into potent activity. The thumb really moves to save itself from collapsing!
One more thing: I noticed my student moving her thumb mostly from the middle joint. When I told her the joint from which the thumb should move is at the wrist, this helped it immediately become effective in its action.
Voila, problem solved – I wish they were all that easy!
AFF