After several years of playing, the felt and cloth parts in a piano will wear down or compress from normal usage. Parts become out of alignment, loose or wobbly, and because of this, the touch of the piano may become inconsistent from key to key. It may feel sloppy, not as responsive as it used to, or no longer as comfortable to play. Other signs are excessive noises such as clicking and squeaking sounds.
The remedy for this is called regulation. The technician will clean and lubricate the action parts. He will also tighten, and align and all the parts to original specifications to optimize repetition and responsiveness.
The amount the piano is played and the ability and sensitivity of the pianist will dictate how often this procedure is needed.
A poorly regulated piano can severely hamper and frustrate a beginner as well as an advanced player, and the player will be amazed at how a little regulation can breathe new life and enjoyment into a piano's touch.