Important new descriptors (Down Force Slope and Up Force Slope), which more fully and meaningfully characterize the continuous Down Force and Up Force are revealed. Similar descriptors are also created to more fully characterize the Balance Force and Frictional Force curves. The invention also discloses various methods and means for accurately testing, measuring and determining other parameters (including the position of the at-rest key, key sluggishness, and others characterizing the “let-off” event) in an accurate and efficient manner. Methods of quantifying and measuring the actual inertia of a key action—in a non-invasive manner—are also disclosed, with several inertial parameters being defined. Methods for quantifying and measuring the actual inertia of the major individual components of a key action are also detailed, along with parameters and methods for expressing their contribution “at the key”. All of the various measurement methods of the current invention are performed in a “controlled, kinetic and continuous” manner.