Piano Technique Reviews: Richard Prokop and Piano Power
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This is not as nutty as it sounds. After all i advocate Using the elbows drawing bone (as an orthographic amplifier of micromovements). If you can use two levers even more back (your torso) good for you. Mini , to micro, to pico, …
For me the torso is restricted to using the intercostals (aka alexander technique) for synchronous belly breathing (synced with a coordinated set of rotations, both left(s) and right(s), or interleaved. This happens to squeeze in the upper arms, which is just another means to influence the elbows.
Just do Chinese calligraphy; or greek clay writing. Advanced virtuoso piano is just those movements, made micro. They are what every 12 year old prodigy uses, having honed his/her reflex bouncing tendons.