An accordion includes a right hand play side, a left hand play side, a bellow provided between the right hand play side and the left hand play side, and four rows of buttons provided on at least one of the right hand play side and the left hand play side. The four rows of buttons include a first column to which first continuous four pitches are assigned, a second column, provided adjacent to the first column, to which second continuous four pitches are assigned, the second continuous four pitches being adjacent to the first continuous four pitches, and a third column, provided adjacent to the second column, to which third continuous four pitches are assigned, the third continuous four pitches being adjacent to the second continuous four pitches.