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How to play a C7 chord on Accordion

AKA: C7, C Dom, C dom7, C Dominant 7th, C Dominant seventh

The 7th chord buttons on Stradella bass system play just the root, the 3rd, and the 7th. The 5th is omitted. In order to play a full dominant seventh chord, instead of using the 7th chord button, you should play the diminished chord right above the root row as shown below.
The diminished chord plays the root, the minor 3rd and the diminished 7th but in this case, they act as a 5th, 7th and major 3rd which added to the fundamental, form a complete dominant 7th chord.
For example:
G7 = G, B, D, F (R, 3rd, 5th, m7th)
Root + 7th chord: G + G7 = G + G, B, F (R, 3rd, m7th)
Root + Dim chord: G + D dim = G + D, F, B (R, 5th, m7th, 3rd)

C7 Accordion chord chart



C, E, G, B♭

C7 button plays:
C, E, B♭ (no G)


R, 3°, 5°, m7°

7th chord buttons play:
R, 3°, m7° (no 5°)

Left hand:

Root + 7th chord: C7(omit5)
C + C7

Root + Dim chord: C7
C + G dim


4 + 2


2 thoughts on “How to play a C7 chord on Accordion”

  1. The 6th chapter shows 6th Major chords.
    Why don’t you show 6th minor chords, please
    Thanks a lot for your very interesting website

    1. Hi Marc,
      thank you so much for your appreciation!
      I avoided listing 6th minor chords because diminished 7th bass chords on the accordion correspond also to Minor 6th chords.
      Take a look at Diminished Chords: “The diminished chord buttons on the accordion actually are diminished 7th chords without the 5th, this means that they play just the root, the minor 3rd, and the diminished 7th (which is also a 6th).”
      For example Cdim = C + Eb + A which is also a Cm6 (5th omit).
      You could play a complete Cm6 (C + Eb + G + A) playing C bass + Cm chord + Cdim chord but I suggest playing just C bass + Cdim chord for both diminished and minor 6th chords.

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