C#aug9

General info

Full name

C# Aug 9

Symbol

C#aug9

Root

C#

Quality

Aug 9

Chord notes

Functions & resolutions

Typical function in key

viRelative tonic (vi)E major

Stability / tension

High tension — requires resolution

Most common resolutions

F#F# MajorD#mD# Minor

Unstable degrees

3F

4F#

resolves up to the resolution tonic

#5A

6A#

resolves up to the tonic 3rd

6A#

b7B

resolves down to the tonic 3rd

Main resolution

C#aug9source

F#F# Major

Dominant 7th C#7 naturally resolves up a 4th to F#. It is the tritone between the chord's 3rd and 7th that creates this pull.

Other resolutions

C#aug9source

Deceptive resolution

D#mD# Minor

Instead of the tonic, the dominant resolves to the vi degree. Creates surprise and is often used to extend a musical phrase.

C#aug9source

Modal resolution

BB Major

In rock and blues, the dominant often moves to bVII or IV instead of the tonic, creating a modal flavor.

C#aug9source

Jazz reharmonization

G7G Dominant 7

Tritone substitution: C#7 can be replaced by G7 (a tritone away). Both chords share the same tritone between the 3rd and 7th, resolving to the same tonic.

C#aug9source

Functional resolution

C#sus4C# Sus4

The dominant can resolve beyond the tonic: moving to IV (subdominant) or to a suspension (sus4) are common alternatives in pop and folk music.

Substitutions

Tritone substitution

G7G Dominant 7

Features

Character

Dominant, with 9th and augmented 5th

Characteristic interval

Augmented 5th (#5), 9th

Description

The augmented 5th destabilises the triadic core, the minor 7th preserves dominant function, and the major 9th extends the chord. The #5 alteration intensifies chromatic voice leading.

Application

• V+ → I in jazz
• Altered blues
• Passing chords

Voicing & structure

Harmony

Compatible scales

All chord tones are contained in these scales — use them for improvisation.