The English concertina was invented by Sir Charles Wheatstone. It is unisonoric, and fully chromatic, so you can play in any key. The true 'concertina' is hexagonal, later a 12 sided version was marketed by the Lachenal company who called it the 'Edeophone'. The Wheatstone company brought out an Octagonal istrument which they called the 'Aeola', although, strictly, the term Aeola was applied to their long series reeded instruments, the first of which were six sided and sported a strange pin hole fretting design. Very soon the 'Aeola' name became linked to the shape rather than the reed form.