Action regulation involves the adjustment of moving parts of the piano that cause strings to sound when a key is played. The purpose of action regulation is to counteract the wear on various wooden, felt, and leather parts due to friction and changes in humidity.

Action regulation is not required as often as tuning, but is nevertheless a vital aspect of piano maintenance. Repetition speed, responsiveness, and even sustain and loudness are all affected by the performance of the action. Action regulation keeps a piano at its optimum performance level.