AKA: Bb7/9/11, Bb9(11), Bb9/11, Bb Dominant 11th, Bb Dominant 7th/9th/11th, Bb Dominant eleventh, Bb Dominant ninth eleventh, Bb Dominant seventh ninth eleventh
Bb11 Accordion Chord Chart
An 11th chord is a chord that includes the root note, the major 3rd, the perfect 5th, the minor 7th, the major 9th, and the perfect 11th.
In terms of music theory, 11th chords are considered to be extended chords because they include notes that go beyond the seventh degree of the scale. They are typically constructed by adding the 11th degree to a dominant 9th chord, which creates a rich, complex sound that is often used in many style of music.
11th Chords on Accordion
On a standard bass accordion, you can play 11th chords by combining a root and its Major chord with the Major chord built on the minor 7th interval.
For example, you can play a C11 (C, E, G, Bb, D, F) combining C Major (C, E, G) with Bb Major (Bb, D, F). Some accordionists may opt for a simpler version that only includes the C and Bb Major chords, omitting the 3rd and 5th notes that don’t add tension to the chord. This is why on the bass chart, the chord button circled in purple is marked as optional.
By playing only the buttons circled in green, you have: Root, 7th, 9th, and 11th which can also be seen as a suspended chord (9sus4).
On the keyboard: an eleventh chord, in theory, has 6 notes, however, since your hand can play only 5 keys at once, you can omit either the root or the 3rd or the 5th with your right hand.
B♭, D, F, A♭, C, E♭
R, 3°, 5°, m7°, 9°, 11°
B♭ + A♭M
(A# + G#M)
same as B♭9sus4
B♭ + B♭M + A♭M
(A# + A#M + G#M)
2 + 4
3 + 2 + 4