The piano action is the mechanical component of a piano. A piano is made up of a harp and a mechanism that strikes the strings of the harp, which is called the action. The action is made up of the keys and a system of moving parts that translates the movement of the keys into movement of hammers that in turn strike the strings. When a piano is new, the action is adjusted so that it will produce the best feel and response that the piano is capable of.
Over time as the action wears in, the felt compacts and the hammers wear, tone and the touch of the piano may start to decline. When this occurs it is time to look at regulating the action and voicing the hammers. Depending on how far the instrument has been allowed to decline this job may take just a few hours or a few days.
As a piano ages the hammers can develop deep ruts where they come in contact with the strings. The hammers may also flatten out and cause a slapping sound when they strike the strings. This causes the piano to sound harsh or metallic. If the hammers are note too worn or too ancient they can be filed to remove some of the felt and restore the original shape. This procedure will always improve the sound of the piano to some extent . Some times however the hammers are too old and worn to produce satisfactory results. When this happens its time to look at replacement.
Replacing old hammers with a set of new, high quality hammers can suddenly bring a piano back to life. Installing new hammers also involves voicing as they may sound too harsh or too soft when they are first installed. It is very rare for a hammers to have an even tone throughout the piano until they have been voiced. All new pianos have had some voicing done to the hammers in the factory. Depending on the quality of the instrument there may still be some room for improvement in the voicing when the piano is uncrated.
When a piano owner is looking at having new hammers installed in their piano it is important to ask the technician about voicing as it is often overlooked and can make all the difference to the end result.