Just caught this on the BBC-- Lubomyr Melnyk developed a way of playing piano at incredible speed with expressiveness, and relates it t'ai chi-- "to play at this speed, your body has to turn to water" (approximate quote).
Here's an a little about his approach, which includes on a soft touch and lack of fear of mistakes. Unfortunately, his book Open Time, is not only out of print, it's not available for sale anyplace I looked.
His work has a lot of overlap with Kenny Werner's Effortless Mastery, if you'd like something in that range for jazz rather than classical.
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