Wheatstone concertina

Wheatstone concertina, mahogany, 24 key, invented 1829, patented 19 December 1829, No 5803, Great Britain, by Charles Wheatsone, a musical instrument having buttons in a rectangular arrangement of four staggered rows, with the short side of the rectangle addressing the wrist. The two innermost rows of the layout constitute a diatonic C major scale, distributed alternately between the two sides of the instrument, C-E-G-B-d is on one side, D-F-A-c-e on the other. The two outer rows consist of the sharps and flats required to complete the chromatic scale.