A hammer sensor of a keyboard musical instrument monitors a hammer action from a home position to a rebounding point on a stopper or strings, and a controller determines a hammer velocity and a time at an intermediate point on a trajectory of the hammer in a recording mode; the controller delays the time so as to determine a key-on timing, and an electronic system reproduce the acoustic or electronic sound at the key-on timing in a playback mode so as to reproduce the acoustic or electronic sound at the same timing as the original sound.