This week there comes a third element in this row: using our entire body when playing, in order to our express our feeling even better.
Last week I was sitting next to a man who played the piano. He played magnificently. But yet it was not perfect. When I was sitting next to him and listened and was impressed and felt with the music the man started to play even more interesting. All of a sudden he seemed to start playing with his entire body. He almost made fists playing the more powerful parts and playing the tender parts he wiggled on his chair smiling.
If you move during playing the piano this influences your playing. If you want to play fast and rhythmical it usually helps to move your FEET and LEGS. Most jazz pianists often not only play the bar with their feet but often even the double tempo so that they can make extra rhythm with their feet during playing the piano. This makes that they can keep the structure and the rhythm even in the faster passages and moreover it embellishes their pedal work, because if you play fast you also have to move the pedal faster otherwise the fast, rhythmical, tones become grinded like an ugly pap.
Another physical support of your playing is working with your FACE. You can start smiling when you play a tender song and you can frown or move your head wildly when you play bombastic passages, you can look over you shoulder to the public for a moment if you play a melody that has something asking in it.
In classical piano-courses students sometimes learn playing according to a method where they have to lift their wrists every two bars and keep their wrists low every two bars, when playing the piano, so that they develop a smooth way of playing. Because the WRISTS and therewith the ELBOWS and ARMS are kept supplely, their playing becomes supplely and smoothly. Being so strict to force to use a method like this does not fit into my point of view, because expressing your feeling en listening and enjoying playing is number 1, but it has to be said that the movement does influence your quality of playing indeed. I think more in terms of tips. By just paying attention consciously to the MOVEMENTS of your body when you play the piano, movements that can support your playing in the direction that you whish, for example rhythmical, tender, dynamical or melancholic, etcetera, your interpretation and performance of playing will improve.
And it is nice if you can express your FEELING using the MOVEMENTS of your ENTIRE BODY when you play the piano, because moving during your playing helps you to make something more beautiful of it, to stir your playing up, to refine it, to empathize as a pianist more in the musical message that you want to express and for the public, to better feel for the story that the pianist tells with his playing and for both of you, in order to experience more TOGETHERNESS when making and listening to the music.