Abstract: A keyboard controlled just intonation computer for electronic organs which automatically responds to correct the larger tuning errors of equal temperament as each interval or chord is played. The logic circuit for this purpose has twelve inputs corresponding to the twelve notes of the chromatic scale. The logic circuit can be interfaced with the keyboard by utilizing keyer voltages from octavely related key switches fanning into each input of the logic circuit through a diode branch circuit. Each of the twelve master oscillators of the organ has a two input tuning means adjusted to lower the frequency of the master oscillator by one seventh of a semitone if one input is energized by an output of the logic circuit or by three tenths of a semitone if the other input is energized. The smaller pitch shift is required for the top notes of major thirds or major sixths, or for the bottom notes of minor thirds or minor sixths.