With time and use the felts and parts of any piano wear out. Older pianos may even have damage from insect or rodent pests and require new felts or parts. Piano mechanisms are delicate and require careful adjustments to the felts, springs and other parts to perform to their best. There can be over a dozen felts in a single typical grand piano key and as many adjustments that must be made. By setting the parts back to original factory specifications the delicate touch needed for artistic playing can be restored.
There are many minor and inexpensive adjustments that can be made that greatly improve the touch or performance of an instrument,