Abstract: A process and apparatus are provided for recording electric signals corresponding to piano key operation and for reproducing the piano key operation. The process includes switching a discrete frequency oscillator corresponding to each piano key, algebraically adding the outputs of each oscillator, filtering the algebraic sum of the oscillator outputs through a low pass filter, recording the filtered signal, reproducing said filtered signal through a high pass filter, detecting each frequency in the high pass filtered signal, and energizing an electromechanical device so as to actuate the piano key which had switched the discrete frequency oscillator.

Abstract: This apparatus pertains to mechanical and electromagnetic apparatus for controlling player piano operation. The conventional player piano paper tape which opens and closes pneumatic holes in a tracker bar is replaced by a valve board and a plurality of electromagnetic valves. Each electromagnetic valve operates to control air passage through one of the holes in the tracker bar.