Stradella bass system

Main article: Accordion
96-button Stradella bass layout on an accordion. C is in the middle of the root note row.

The Stradella Bass System (sometimes called standard bass) 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 (I, IV and V) in three adjacent columns. In a typical layout, as pictured, each column contains, in order:

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

Each bass note, and each pitch in a chord, is usually sounded simultaneously in multiple octaves. Larger accordions offer some control over the voicing with register switches.[1]

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,[1] 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.


When naming chord buttons, major chords are often suffixed with "M", for example "CM", to distinguish them from bass notes.

In staff notation, notes below the center of the bass-clef staff are bass notes, and notes above the center of the staff usually indicate chord buttons, labeled as necessary with "M", "m", "7", or "d" or "dim".

Within this convention, the written octave for bass notes is arbitrary, as the Stradella system does not have buttons for higher and lower octaves.

An example:

As written:

\clef bass
\time 4/4
c4 c'^"M" e,-- c' g, g <c c'>2

As sounded, with one possible octave voicing:

\clef bass
\time 4/4
<c, c c'>4 <c' e' g> <e, e e'> <c' e' g> <g, g> <d'g b> <c, c c' e' g>2

Bass notes to be played on the major-third (counterbass) row are indicated by repurposed "tenuto" lines below the notes (as in the E bass note in the example above), or underlined note names or numbers.

Single-note bass lines are often labeled "B.S." (bass solo or bassi soli), especially when they extend above the middle of the staff.


As with the piano, fingers are numbered 2 to 5, starting with the index finger, mirroring right-hand fingering. As a rule, the thumb, numbered 1, is not used.

Patterns can be played identically in any desired key, changing only the starting position; this is because unlike a piano keyboard, the Stradella layout does not distinguish between "naturals" and "sharps".

Bass and chords

4-3 is a recommended fingering for a bass note and its corresponding major chord (e.g. C-CM-C-CM).[2] For alternate bass with the root and fifth, 4-3-2-3 can be used for major chords (e.g. C-CM-G-CM), 4-2-3-2 for minor and other types of chords (e.g. C-C7-G-C7).


Scales, runs, and other bass lines are played on the bass note buttons, the row or rows closest to the bellows (root row, optional thirds row, optional minor thirds row).

Major scales

The major scale can be fingered without stretching the hand, playing "do re mi fa sol la ti do" in any key as r4 r2 t4 r5 / r3 t5 t3 r4 (r = root row, t = thirds row) or, with minimal movement of the index finger, r3 r2 t3 r4 / r2 t4 t2 r3.

\new Staff \with { \remove "Time_signature_engraver" }
\relative c, { 
\clef bass
\set fingeringOrientations = #'(down)
 <c-3> <d-2> <e---3> <f-4> <g-2> <a---4> <b---2> <c-3>
 <b---2> <a---4> <g-2> <f-4> <e---3> <d-2> <c-3> 

Minor scales

A recommended fingering for harmonic minor:[3]

\new Staff \with { \remove "Time_signature_engraver" }
\clef bass
\set fingeringOrientations = #'(down)
 <a,---4>^"B.S." <b,---2> <c-3> <d-2> <e---4> <f?-5> <gis---2> <a-3> <gis---2> <f-5> <e---4> <d-2> <c-3> <b,---2> <a,---4>

Melodic minor (different ascending and descending):

\new Staff \with { \remove "Time_signature_engraver" }
\clef bass
\set fingeringOrientations = #'(down)
 <a,---4>^"B.S." <b,---2> <c-3> <d-2> <e---4> <fis---3> <gis---2> <a-3> <g!-4> <f!-5> <e---4> <d-2> <c-4> <b,---3> <a,-2>

Register switches

Larger and more expensive accordions may have as many as seven register switches on the Stradella bass side, controlling the octaves and voicing of the bass notes and chords, similar in concept to the treble register switches.[1] Smaller or simpler accordions may have no bass switches, or a single switch that toggles between two settings.

Bass register switches and reed sets of a typical professional-grade accordion[1]
Register Switch Reed Sets
Soprano Alto Contralto Tenor Bass
C5-B5 C4-B4 F3-F4 C3-B3 C2-B2
(chords and bass notes) (bass notes only)
Soprano S
Alto S A
Tenor S A T
or Bass Forte

Soft Bass
or Bass Piano

Soft Tenor



With the Soprano or Alto register selected, bass buttons exactly duplicate individual notes from the chords, without the usual added lower octaves.

An accordion with two register switches on the bass side might provide Tenor and Master registers, while accordions with additional switches might have larger subsets taken more-or-less from the middle of the table above.[4]

Common configurations

Name Columns Rows of bass-notes Rows of chords
8-bass 4 - Root notes: F to D Root note Major
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 Major 3rd note, root note Major, minor, 7th
48-bass 8 - Root notes: E♭ to E Major 3rd note, root note Major, minor, 7th, diminished
12 - Root notes: D♭ to F♯ Major 3rd note, root note Major, minor
60-bass 12 - Root notes: D♭ to F♯ Major 3rd note, root note Major, minor, 7th
72-bass 12 - Root notes: D♭ to F♯ Major 3rd note, root note Major, minor, 7th, diminished
80-bass 16 - Root notes: C♭ to G♯ Major 3rd note, root note Major, minor, 7th
96-bass 16 - Root notes: C♭ to G♯ Major 3rd note, root note Major, minor, 7th, diminished
120-bass 20 - Root notes: Low A to A♯ Major 3rd note, root note Major, minor, 7th, diminished
120-bass 20 - Root notes: Low A to A♯ Minor 3rd, major 3rd, root note Major, minor, 7th
140-bass 20 - Root notes: Low A to A♯ Major 3rd note,[notes 1] root note Major, minor, 7th, diminished, augmented[notes 1]
160-bass 20 - Root notes: Low A to A♯ Three major 3rd rows, root note Major, minor, 7th, diminished

See also


  1. 1 2 140-bass accordions may come with either an extra minor 3rd note row, located above the regular major 3rd row and the root note, or an augmented 7th chord row.


  1. 1 2 3 4 Balestrieri, Donald (1979). "Registers of the Standard Stradella Keyboard". Accordions Worldwide. Retrieved 24 August 2014.
  2. Zucco, Frank (1985). Mel Bay's Deluxe Accordion Method. Pacific, Mo.: Mel Bay Publications. ISBN 978-0871667823.
  3. Dahl, Gary (2004). Mel Bay's Master Accordion Scale Book With Jazz Scale Studies. Pacific, Mo.: Mel Bay Publications. ISBN 978-078666708-6.
  4. "Accordion Anatomy". Western New York Accordion Club. See diagram "Bass Reed Switches". Retrieved 30 May 2015.

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