Action

Part three:  being an examination of the many parts of my piano's action that I never gave any thought to.  Here's something that seems obvious in retrospect:  the piano has to be constructed so that depressing a key makes a hammer not just land on a string but strike it and immediately rebound; otherwise all that happens is a dull thud.  At the moment of the "strike" the hammer has become a free projectile.

At about the turn of the 18th century, a bright fellow named Bartolomeo Cristofori worked out the piano action that allowed musicians to produce both soft (piano) and loud (forte) notes by striking strings instead of plucking them harpsichord-style.  His early model embodied many principles still in use, such as the interaction of levers to translate a small finger motion into a larger percussive impact on a string some distance away, and a mechanism to keep the hammer from bouncing and restriking, called an "escapement."  The original single-escapement device was improved by the nineteenth-century double-escapement, which allowed the musician to repeat notes very quickly without waiting for the key to come fully back to its resting position.

Among the prized characteristics of a good piano action are the immediacy of the connection between the key and the string (no simple matter considering the Rube-Goldberg intervening mechanism), the smoothness of the action throughout the range of motion of the key, and the responsiveness of the key to the whole range of volume from piano to forte.

Pictured below is a grand-piano action.  For some reason, it never occurred to me before this instant that a grand piano hammer strikes from below the string, even though that should have been clearly visible to me all along; it's right out there in the open.  The link above at "double-escarpment" provides the key for all the little parts as well as helpful animations.

What should piano actions be made of?  Some experts are coming around to the acceptance of composite materials instead of wood.  In that connection, I was surprised to read this expert's glowing praise of a brand I've never heard of:  the Fazioli piano, apparently outstanding for all of its sound qualities, not just the superb responsiveness of its action.