are being expanded or contracted. This is similar to the harmonica, where the note changes depending on whether the player is breathing in or out. 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. The diatonic button accordion is the most popular type of button accordion, and appears in many cultures, especially in folk music.

One popular type of diatonic