The accordion is a box-shaped musical instrument of the bellows-driven free-reed aerophone family, sometimes colloquially referred to as a squeezebox. A person who plays the accordion is called an accordionist.
The instrument is played by compressing or expanding the bellows whilst pressing buttons or keys, causing valves, called pallets, to open, which allow air to flow across strips of brass or steel, called reeds, that vibrate to produce sound inside the body.[notes 1]
A diatonic button accordion (DBA) is a member of the free-reed aerophone family of musical instruments. It is a type of button accordion on which the melody-side keyboard contains one or more rows of buttons, with each row producing the notes of a single diatonic scale. The buttons on the bass-side keyboard are most commonly arranged in pairs, with one button of a pair sounding the fundamental of a chord and the other the corresponding major triad (or, sometimes, a minor triad).
Diatonic button accordions are popular in many countries, and used mainly for playing popular music and traditional folk music, and modern offshoots of these genres.
The accordion is often used in folk music in Europe, North America and South America, and in some countries, such as Brazil and Mexico, it is also commonly used in mainstream pop music. In Europe and North-America, it is often associated with busking. Some popular music acts also make use of the instrument. Additionally, the accordion is sometimes used in both solo and orchestra performances of classical music.
The oldest name for this group of instruments is actually harmonika, from the Greek harmonikos, meaning harmonic, musical. Today, native versions of the name accordion are more common. These names are a reference to the type of accordion patented by Cyrill Demian, which concerned "automatically coupled chords on the bass side".