A concertina is a free-reed musical instrument, similar to an accordion, that is played by expanding and contracting its bellows while pressing buttons or keys. It typically has a hexagonal shape and produces sound through metal reeds that vibrate when air passes over them. Concertinas are popular in various musical genres, including folk and traditional music. The instrument comes in different types, such as the English concertina, which has a uniform layout of buttons, and the Anglo concertina, which has a different layout for each hand. Concertinas are often used in ensembles and can be found in the music of cultures around the world, including Irish and British folk traditions.