A type of accordion in which the melody-side keyboard consists of a series of buttons. This differs from the piano accordion, which has piano-style keys. The sound from the instrument is produced by the vibration of air in reeds. The button accordion is often confused with the concertina, but its buttons are on the front of the instrument, whereas those of the concertina are on the sides and pushed in parallel with the bellows.

All accordions and concertinas have 3 main components: reeds, bellows and buttons or keys. Pushing or pulling the bellows slower or faster makes the sound softer or louder, respectively. The button accordion has free reeds on both the treble and bass sides. The press of a button opens a valve to allow air to pass through the reed or reeds to make a sound when the bellows are pumped in or out. The button accordion has melodic notes on one side of the bellows (usually the right side) and bass accompaniment notes on the other side (generally the left).

There are 2 main types of button accordion:

• the diatonic button accordion has reeds fixed in pairs and is bisonoric so that one note sounds when air moves in and a different one when air moves out, similar to the harmonica. In most diatonic button accordions, each row of melody buttons produces a different major scale, with accidentals on 'helper buttons' at the ends of the rows. It is the most popular type of button accordion and appears in many cultures, especially in conjunto, Tejano and other folk music.
• The chromatic button accordion is very similar to the piano accordion, but can have 3, 4 or 5 rows of buttons on the right hand side. It is unisonoric, meaning the same note is sounded whether the bellows are pushed or pulled. The chromatic button accordion is traditionally used in a concert setting and is more popular in jazz and classical music because it can be freely played in any key, usually with identical fingering patterns.