The accordion is a portable instrument that has two keyboards - usually one similar to the piano's, and another one consisting of buttons - connected by bellows.
When the instrument's bellows are activated by the musician's left hand, the resulting air flow stimulates the vibration of free reeds, made of tempered steel, located inside the instrument.
The left hand of the musician also handles the bass keyboard. Formed by buttons, it can produce both simple notes and determined chords. As to the right hand, it controls the treble keyboard, piano-like and responsible for the playing of the melody.
It was invented by the german Christoph Ludwig Buschmann in 1821 and developed by the austrian Cyrillus Demian in 1829. It was originated of its most primitive ancestral, the millenial chinese instrument Sheng.
In Brazil, it was introduced by german and italian immigrants. It became popular through Luiz Gonzaga, a musician from the north-east of Brazil that also spreaded a different word to call the accordion: sanfona.
Luiz Gonzaga and his sanfona - Luiz Gonzaga Memorial - Recife - Pernambuco
Although the sanfona is currently related to brazilian northeastern music, 20th century composers such as Alban Berg and Sergei Prokofiev have it included in important pieces.