6-plus-6-instruments

6-plus-6-instruments are musical instruments having each 12 tones. Their keys or cords are in two rows. In each row the tone distance is a whole-tone distance. The distance between both rows is a half-tone distance. So there is the same fingering in all 6 scales where the base tone is in the same row. If there is a third row, which is the same like the first row, there is the same fingering in all 12 scales, e. g. on a piano with a Janko keyboard.

A Janko keyboard.