In the balancing of piano key mechanisms according to the invention, counterweights are placed in each piano key to balance said key mechanism in order to create a smooth linear progression of key front weights along a keyboard, thereby providing a keyboard with a more uniform "feel" to the piano keys...http://www.google.com/patents/US5585582?utm_source=gb-gplus-sharePatent US5585582 - Methods for inertial balancing of piano key mechanisms
