Just intonation electronic keyboard instrument

摘要

A just intonation electronic keyboard instrument comprises a plurality of tonality selection switches for selecting each key from among twenty-four just intonation keys, a control circuit for determining one or a plurality of just intonation keys according to the manipulation of said switches, a variable frequency oscillator having its output oscillation frequency varied in accordance with the selected key, and a frequency dividing circuit having frequency dividers which are varied of their frequency dividing ratios according to the selected key. The number of tonality selection switches is less than twenty-four. The control circuit discriminates the selection to a major scale or a minor scale, and discriminates one or a plurality of keys from each of twelve keys from C through B, and determines one or a plurality of selected just intonation keys, according to the manipulation of said intonation selection switches. The variable frequency oscillator produces an output oscillation frequency which is an integral multiple of a frequency of a key-note of the determined key. The frequency dividing ratios of the frequency dividers are respectively varies so that ratios among frequency dividing ratios are in accordance with a temperament of the determined just intonation key.