Stradella bass system

The Stradella Bass System (sometimes called "standard bass") is a buttonboard layout equipped on the bass side of many accordions, which uses rows of buttons arranged in a circle of fifths; this places the principal major and minor chords of a key (I, IV and V) in three adjacent rows. Each row contains, in order:
* The major third above the root ("counter-bass")
* The root note
* The major chord
* The minor chord
* The dominant seventh chord
* The diminished seventh chord

The following chart shows a standard 120-button Stradella layout.

In modern accordions, each chord button sounds three individual pitches. Early accordions sounded four pitches for the seventh and diminished chords. Modern Stradella systems omit the 5th from these two chords, allowing for more versatility. For example, an augmented seventh chord can be created by using the dominant seventh chord button and adding an augmented 5th from the right-hand manual or from one of the bass or counterbass buttons.

In most Russian layouts the diminished seventh chord row is moved by one button, so that the C diminished seventh chord is where the F diminished seventh chord would be in a standard Stradella layout; this is done in order to achieve a better reachability with the forefinger.

Register switches

The larger and more expensive accordions can also have on the Stradella bass side, some Register switches, similar in concept to the treble register switches

Common configurations

Notes