The bandoneón is regarded as the signature instrument of the tango. It is a free reed instrument with 5 rows of finger buttons on each side. It is notoriously difficult to play, as the pitch is different on the left and right sides, and varies when closing the bellows in, or opening them out.
The bandoneón was originally conceived in 1840s Germany by Heinrich Band as a portable organ for use in outdoor weddings, processions and religious festivals, or for ease of use in the remote regions of the New World. Production began around 1849 in Carlsfeld by the manufacturer Carl Zimmermann. The factory manager, Ernst Louis Arnold (ELA bandoneóns) and later his sons, Ernst Hermann, Alfred and Paul (AA, A, Premier and Alfa bandoneóns) took over the business. The factory continued to produce bandoneóns until 1959.