A chromatic button accordion is a type of button accordion where the melody-side keyboard consists of rows of buttons arranged chromatically. The bass-side keyboard is usually the Stradella system or one of the various free-bass systems. Included among chromatic button accordions are the Russianbayan and Schrammel accordion. There can be 3 to 5 rows of horizontal treble buttons. In a 5 row chromatic, two additional rows repeat the first 2 rows to facilitate options in fingering.
Comparing the layout to the piano accordion
Throughout former Yugoslavia a 6-row chromatic button layout is used based on the B system. It is referred to as dugmetara.