A 120 bass accordion chart is a diagram that shows the layout of all 120 bass buttons on a standard accordion.
These buttons are organized using the Stradella bass system, which groups bass notes and chords by musical function.
Each of the 120 buttons plays either:
- A single bass note
- A major chord
- A minor chord
- A dominant 7th chord
- A diminished chord
This powerful layout lets accordionists play complete accompaniment with just one hand.
Understanding the Stradella Bass System
The 120 bass system uses 6 horizontal rows and 20 vertical columns, arranged by the circle of fifths.
The 6 Rows (from top to bottom):
- Counterbass Row – notes a major third above the bass row
- Bass Row – fundamental bass notes (C, G, D, A, E…)
- Major Chord Row – C, G, D, A, E major
- Minor Chord Row – Cm, Gm, Dm, Am, Em
- Seventh Chord Row – C7, G7, D7, A7, E7
- Diminished Chord Row – Co, Go, Do, Ao, Eo
Each column corresponds to a musical key family (C column, G column, D column, etc.).
120 Bass Accordion Chart (Full Standard Layout)
Below is the complete Stradella layout most 120-bass accordions use:
COUNTERBASS C G D A E B F# Db Ab Eb Bb F C G D A E B F# Db
BASS C G D A E B F# Db Ab Eb Bb F C G D A E B F# Db
MAJOR CHORD C G D A E B F# Db Ab Eb Bb F C G D A E B F# Db
MINOR CHORD Cm Gm Dm Am Em Bm F#m Dbm Abm Ebm Bbm Fm Cm Gm Dm Am Em Bm F#m Dbm
7TH CHORD C7 G7 D7 A7 E7 B7 F#7 Db7 Ab7 Eb7 Bb7 F7 C7 G7 D7 A7 E7 B7 F#7 Db7
DIMINISHED Co Go Do Ao Eo Bo F#o Dbo Abo Ebo Bbo Fo Co Go Do Ao Eo Bo F#o Dbo
This chart repeats after 20 columns to give you 120 total bass buttons. During warm-ups, the Pitch Detector helps singers adjust their tone before performing.
How to Read the 120 Bass Chart
Vertical Movement = Same Key Family
Example (C column):
- Counterbass = E
- Bass = C
- C major
- C minor
- C7
- C diminished
All buttons relate to the C family.
Horizontal Movement = Circle of Fifths
Moves in perfect fifths: C → G → D → A → E → B → F# → Db → Ab → Eb → Bb → F → C …
This makes chord progressions extremely easy.
Why the 120 Bass System Is So Effective
Fast Key Changes
Easily move right/left to switch keys.
Full Harmonic Control
All major, minor, 7th, and diminished chords are available instantly.
Efficient Hand Position
Entire accompaniment patterns can be played without shifting the hand.
Ideal for All Genres
Perfect for folk, jazz, tango, classical, musette, polka, zydeco, and pop.
How to Use the 120 Bass Accordion Chart for Practice
1. Practice I–IV–V Progressions
Example in C major:
C → F → G
2. Use Bass + Chord Patterns
C (bass) → C major
G (bass) → G major
3. Walk Bass with Counterbass
C → E → G → B → D → F# → A
4. Practice Minor Key Progressions
Am → Dm → E7
Beginner Tips for Learning 120 Bass Buttons
Start with the C Column
Your “home base” row.
Memorize the Order of the Rows
Counterbass → Bass → Major → Minor → 7th → Diminished
Use Touch Landmarks
Some accordions have tactile bumps on C and E-flat buttons.
Learn the Circle of Fifths
This unlocks instant chord progressions.
FAQs
How many buttons does a 120 bass accordion have?
It has 120 buttons arranged in 6 rows and 20 columns.
What system does a 120-bass accordion use?
The Stradella bass system.
Which chords can you play on a 120-bass accordion?
Major, minor, seventh, and diminished chords for all keys.
Why does the layout follow the circle of fifths?
To make key changes and chord progressions smoother and more intuitive.
Is a 120-bass accordion good for beginners?
Yes, it is the most common and versatile type for learning and performing.
Conclusion
The 120 bass accordion chart is the heart of the Stradella bass system, giving players instant access to bass notes, major/minor chords, seventh chords, and diminished chords.