QUOTE(chocolatedog @ Aug 18 2006, 05:19 PM)

It sounds too simplistic to me....
Me too. I have a glorious mental picture of wrists describing contrary motion semi-circles, regardless of what the player
actually has to play. Hysterical.
Arm\wrist movement depends entirely on what the pianist has to achieve.
Take a short run of notes - say C,D,E,F,G. A movement of the wrist in the direction of travel helps. If this pattern is repeated, then a sort of circular movement will result because the wrist will have to return to its starting position. A brilliant example of this is a lh passage from Beethoven't Waldstein sonata, first movement, development section. The left hand has to play a repeated semiguaver GCBA passage for what feels like forever. A circular wrist movement helps hugely here.
Or take a standard Alberti bass. A slight wrist rotation in the direction the notes travel helps a lot.
How about the Chopin Op 25 no 1 study? (Ab - Aeolian Harp) The lh covers huge amounts of space with a forearm-leading-the-wrist movement always in the direction of travel of the notes - side to side rather than circular. Meanwhile, the rh is performing a sort of reverse Alberti bass type movement.
I could go on, but there is no need, because there is a basic principle we can all usefully observe: the wrist travels so as to lie behind the finger actually playing the note, giving that finger support. This movement does not obviate finger action - strong, clean articulation is vital for pianists - but it sure helps a lot.