An automatic player piano is fabricated on the basis of an acoustic piano, and an automatic player is expected to give rise to key motion for reenacting performance with solenoid-operated key actuators; since the hammers of acoustic piano are different in mass, the load against the key motion is also different among the keys; while the motion controller is forcing the keys to travel on reference key trajectories through a servo control loop, the motion controller takes the pitched part into account, and selectively accesses control parameter tables so as to read out the approximate control parameters for the individual keys, whereby the hammers surely reach the target final hammer velocity before striking the strings.