An automatic player piano includes key sensors, solenoid-operated key actuators and a controller, which form a servo-control loop, and the key motion is reproduced under the control of the servo-control loop; the servo-control loop adjusts the driving pulse signal to a target duty ratio or mean current so as to force the black and white keys to travel on reference key trajectories; the controller categorizes the key motion in half-stroke or full-stroke, and determines the target duty ratio on the basis of a deviation between the target key position and the actual key position, a deviation between the target key velocity and the actual key velocity and the sort of key motion so as to make the key motion stable.