White Keys and Black Keys -- Again and Always

This morning my wonderful scientist-student, struggling to get the proportions correct in her Haydn D major sonata noticed something critical:

It begins with a prominent white key. all by itself, answered soon by a black key, again by itself, then two corresponding white keys.  After the double bar, however, a recognizably similar figure comes in: black key, signalling that we are in deep trouble as the bizarre colors thrown off by these intrusive sounds bewilder the ear, thickening the plot at an alarming pace.

Knowing theory, as I do (she far less) and knowing abstract sonata-form structure, as I do, alas (she far, far less) I am less observant than she of the shock engendered by such radical procedures.  Yet deep down I know that this power explains the surge of interest in the sonata form contemporary with the development of the piano.

It is a question of the acoustical impact of the short lever (black key) in contrast with the long (white key).

In the several conversations I had at a recent get-together of early music people none had ever heard of this dynamic aspect of piano playing.

Curious.  Once aware of it the delight is endless of fooling around with fingering, hand position, attack and release impact, and so on.  It certainly gets me up in the morning.