A Day On Wikipedia

{{main|Accordion}}
The ”’Stradella Bass System”’ (sometimes called ”standard bass”) is a [[musical keyboard|keyboard]] layout equipped on the bass side of many accordions. uses rows of buttons arranged in a [[circle of fifths]]; this places the principal major 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 [[Seventh chord#Dominant seventh|(dominant) seventh chord]]
* The [[diminished seventh]] chord

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

[[Image:120-button_Stradella_chart.svg|thumb|center|700px]]

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.

===== Common Stradella configurations =====
{| class=’wikitable’ width=’75%’
! Name !! Columns !! Rows
|-
! 12-bass
| 6 – Root notes: B♭ to A || Root note, major
|-
! 24-bass
| 8 – Root notes: E♭ to E || Root note, major, minor
|-
! 32-bass
| 8 – Root notes: E♭ to E || Root note, major, minor, 7th
|-
! 40-bass
| 8 – Root notes: E♭ to E || Counter-bass note, root note, major, minor, 7th
|-
! rowspan=2 | 48-bass
| 8 – Root notes: E♭ to E || Counter-bass note, root note, major, minor, 7th, diminished
|-
| 12 – Root notes: D♭ to F♯ || Counter-bass note, root note, major, minor
|-
! 60-bass
| 12 – Root notes: E♭to F♯ || Counter-bass note, root note, major, minor, 7th
|-
! 72-bass
| 12 – Root notes: D♭ to F♯ || Counter-bass note, root note, major, minor, 7th, diminished
|-
! 80-bass
| 16 – Root notes: C♭ to G♯ || Counter-bass note, root note, major, minor, 7th
|-
! 96-bass
| 16 – Root notes: C♭ to G♯ || Counter-bass note, root note, major, minor, 7th, diminished
|-
! 120-bass
| 20 – Root notes: Low A to A♯ || Counter-bass note, root note, major, minor, 7th, diminished
|-
! 140-bass
| 20 – Root notes: Low A to A♯ || Counter-bass note, root note, major, minor, 7th, diminished, augmented (or extra counter-bass note – if present will be between root and counter-bass-1)
|-
! 160-bass
| 20 – Root notes: Low A to A♯ || Three counter-bass notes, root note, major, minor, 7th, diminished
|}