The C♯ Dominant 9th chord is a five-note chord made up of C♯, E♯, G♯, B, and D♯. It is built from a root, major third, perfect fifth, minor seventh, and major ninth.
Construction
C♯ Dominant 9th = Root + Major 3rd + Perfect 5th + Minor 7th + Major 2nd = C♯ · E♯ · G♯ · B · D♯
| Note | Interval | Degree |
|---|---|---|
| C♯ | Root | 1 |
| E♯ | Major 3rd | 3 |
| G♯ | Perfect 5th | 5 |
| B | Minor 7th | ♭7 |
| D♯ | Major 2nd | 9 |
Key Signature
A dominant chord points home to the key a fifth below its root: the C♯ Dominant 9th is the V (dominant) of F# Major, so the relevant key signature is that key’s — 6 sharps (F♯, C♯, G♯, D♯, A♯, E♯). Spelled as a scale, these notes are C# Mixolydian.
F♯C♯G♯D♯A♯E♯
Order of sharps
Sharps are added to a key signature in a fixed order. Each new sharp key adds the next sharp on the list.
F♯C♯G♯D♯A♯E♯B♯
Mnemonic: Father Charles Goes Down And Ends Battle
Chords in the Key of F♯ Major
These are the triads built on each degree of the F♯ major scale:
C♯ Dominant 9th — Frequently Asked Questions
What is the C♯ Dominant 9th chord on piano?
The C♯ Dominant 9th chord contains the notes C♯ – E♯ – G♯ – B – D♯. On piano, play these notes together to sound the chord.
What notes are in the C# Dominant 9th chord?
The C# Dominant 9th chord (C#9) contains 5 notes: C#, F, G#, B, D#. Formula: R-M3-P5-m7-M9.
How is C#9 used in music?
C#9 is used in jazz, fusion, and contemporary music to add harmonic color. It appears as a dominant or tonic chord depending on context.
What is the scale degree formula for C#9?
C#9 uses scale degrees 1-3-5-b7-9, giving it its distinctive sound.