The Stradella Bass System is a buttonboard layout equipped on the bass side of many accordions, which uses columns of buttons arranged in a circle of fifths; this places the principal major chords of a key in three adjacent columns.

A free-bass system is a system of left-hand bass buttons on an accordion, arranged to give the performer greater ability to play melodies with the left-hand and form one's own chords. The left-hand buttonboard consists of single-note buttons with a range of three octaves or more, in contrast to the standard Stradella bass system, which offers a shorter range of single bass notes, plus preset major, minor, dominant seventh, and diminished chord buttons. The term "free-bass system" refers to various left-hand manual systems that provide this functionality: The Stradella system does not have buttons for different octaves of the bass notes, which limits the types of melodies and basslines that can be performed with the left hand.