AKA: C9 sus4, C ninth suspended fourth, C9sus, C nine suspended, C Dominant ninth suspended 4
C9sus4 Chord on Accordion
These chords can add a sense of tension and resolution to a musical phrase and are often used to create movement and interest in a chord progression. Sus4 chords are chords that are built by replacing the 3rd note of the scale with the 4th note. A 9sus4 chord is a type of suspended chord that is built by adding the 7th and the 9th note of the scale to a sus4 chord.
For example, in the key of C, a Csus4 chord would consist of the notes C, F, and G, with the F replacing the E that would be in a standard C major chord. A 9sus4 chord would add the Bb (7th) and the D (9th) to the Csus4 chord, resulting in the notes C, F, G, Bb, and D, which are root, perfect 4th, perfect 5th, minor 7th and major 9th intervals.
9sus4 Chords on Accordion
On a standard bass accordion, 9sus4 chords are actually 9sus4(5omit) because there is no button combination that allows for the creation of a complete 9sus4 chord that include the 5th (which btw doesn’t add any tension to the chord). This chord is the best option available on the Stradella system to play a suspended chord.
A 9sus4(5omit) chord can be created by combining a root note with the Major chord built on its minor 7th interval.
For example, combining the root note C with the Bb Major chord (since Bb is at a minor 7th interval from C) results in an C9sus4(5omit) chord, which is formed by the notes C, F, Bb, and D (root, perfect 4th, minor 7th, and 9th). To simplify the nomenclature, we avoid mentioning the missing 5th every time we mention this chord, just remember it.
It’s very similar to a ninth eleventh chord but it does not have either the 3rd nor the 5th and the 11th is seen as a 4th.
C, F, Bb, D
R, 4°, m7°, 9°
C + B♭M
2 + 4
3 + 5