In a player piano, a position sensor is provided on an end portion of a lifting rail for detecting a vertical position of the lifting rail. In storing performance data of dampers, a signal output from the position sensor and indicative of a vertical position of the lifting rail is converted into a digital signal, and a position value indicative of the position of the lifting rail is generated on the basis of the digital signal and stored into a buffer. A conversion section converts the position value into a vertical position of a pedal rod connected to a damper pedal, and the thus-converted vertical position is converted, into a control value which a control change message of the damper pedal in MIDI-format data can take. The control value obtained in the aforementioned manner can be recorded into a recording medium as performance information.