Anglo concertina

Introduction
The Anglo-German concertina originated when the bisonoric arrangement of early German concertinas was adapted to the construction style of the English concertina.

History
The first instruments had 20 buttons, arranged in two rows per side, with the rows playing in keys a fifth apart.

Though the 2-row instruments are still made, the "Anglo," as it came to be called, underwent development similar to that which occured with German concertinas. The two "home" keys remain, but larger instruments are capable of a full chromatic scale on both press and draw in the right hand. Aside from the central row however, the layout is quite different from the German concertinas.