Wicki-Hayden note layout

In music, the Wicki-Hayden note layout has the same advantage over the traditional keyboard layout as the 6-plus-6-system: There is the same fingering in all 12 scales. It is used for the Hayden duet concertina. Kaspar Wicki patented it in 1896 in Switzerland. Brian Hayden, a concertina player, refined this layout and patented it again in 1986 in Great Britain.