F# Added 9th Chord
Chord Tones: F# Added 9th Chord
Symbol: add9, add2 — Formula: 1-3-5-9
| Degree | Note | Frequency (A=440, Equal) |
|---|---|---|
| 1 | F# | 369.994 Hz |
| 3 | A# | 466.164 Hz |
| 5 | C# | 277.183 Hz |
| 9 | G# | 415.305 Hz |
Chord Notation
| Notation Type | Symbol / Value |
|---|---|
| Lead Sheet Symbol | F#add9 |
| All Common Symbols | add9, add2 |
| Interval Formula | 1-3-5-9 |
| Harmonic Category | bright |
Roman numeral (e.g. I, IV, V) and Nashville Number notation are key-dependent. See Keys pages for chord function within specific keys.
Inversions
| Inversion | Notes (low to high) | Bass Note | Slash Notation |
|---|---|---|---|
| Root Position | F# – A# – C# – G# | F# | F# Added 9th Chord |
| First Inversion | A# – C# – G# – F# | A# | F# Added 9th Chord/A# |
| Second Inversion | C# – G# – F# – A# | C# | F# Added 9th Chord/C# |
| Third Inversion | G# – F# – A# – C# | G# | F# Added 9th Chord/G# |
Harmonic Function
The F# add9 chord commonly functions as the tritone substitution in C major or tonic in F# major. Its harmonic role varies by key — in major keys it provides stable harmonic grounding.
The add9 chord adds a ninth (octave + second) to a major triad without including the seventh. It has a bright, open sound, richer than a plain major chord but less complex than a major ninth.
Common Progressions
The F# Added 9th Chord frequently appears in these progression patterns (shown in Roman numeral notation relative to key):
Iadd9-IVadd9Iadd9-V
Songs Featuring the Added 9th Chord
Well-known songs where the F# Added 9th Chord — or this chord type — plays a prominent role:
- Every Breath You Take – The Police
- With or Without You – U2
- Right Here Waiting – Richard Marx
Tuning Frequencies Across Temperaments
Frequencies shown at A=440 Hz. View full temperament data for any note.
| Note | Equal Temp. | Pythagorean | Just Intonation |
|---|---|---|---|
| F# | 369.994 Hz | 371.251 Hz | 367.911 Hz |
| A# | 466.164 Hz | 463.538 Hz | 470.926 Hz |
| C# | 277.183 Hz | 278.437 Hz | 279.067 Hz |
| G# | 415.305 Hz | 417.657 Hz | 418.601 Hz |
Scales Containing the F# Added 9th Chord
These scales include the F# Added 9th Chord as a diatonic or characteristic chord: