The document summarizes key details about accordions, including that they are portable box-shaped instruments with bellows that are played by pressing buttons or keys to allow air to flow across brass reeds and produce vibration. Accordions are commonly used in folk music in places like the Basque Country and Europe and North America. Accordions come in different configurations including bisonoric and unisonoric types, and have a body made of two wooden boxes joined by bellows. The accordion was invented in 1822 in Berlin and became popular in music between 1900-1960s, considered the golden age of the accordion.