Ohlsson on Chopin Op. 10, No. 1
This is a wonderful lesson, and I say that as one who is about as far from ever attempting that piece as I am from flying to Jupiter. (Maybe if I were about 50 years younger...) His discussion of the release of muscular tension, the involuntary action of the thumb when opening the hand, and related fundamentals will serve virtually any pianist who has developed beyond early children's pieces.
One of my own exercises uses some the same principal. Parallel octaves on C and E in the L and R hand, respectively, the right hand an octave above the left, starting on C 2 octaves below middle C, playing C (as designating the low note), C', C', C'', C',C', C. Thumb to pinky, thumb repeating the pinky's note, then the reverse on the way down. Pretty basic, but a simple open-close action to maintain relaxation along the lines Mr. O. discussed. Of course, he elaborates far more -- and so enjoyably.
Thank you, Tonebase and Mr. Ohlsson.