Intervals
Augmented Ninth
9A · 15 semitones
An augmented ninth is an octave plus an augmented second — {semitones} semitones in all.
Also written A9 · 9A
Augmented Ninth
9A · 15 semitones
On the piano, from every note
| From | Notes | Play it on your instrument |
|---|---|---|
| C | C – D# | |
| C# | C# – D## | |
| D | D – E# | |
| Eb | Eb – F# | |
| E | E – F## | |
| F | F – G# | |
| F# | F# – G## | |
| G | G – A# | |
| Ab | Ab – B | |
| A | A – B# | |
| Bb | Bb – C# | |
| B | B – C## |
Tap a key or a fret to hear it.
- DLetter
- ELetter
- FLetter
- GLetter
- ALetter
- BLetter
- CLetter
15 semitones
Read on: number and quality · inversion · compound intervals · consonance and dissonance
Every ninth
A ninth can take these qualities, one semitone apart; choose one to see the upper note move and hear the pair.
Understanding Augmented Ninth
Names and symbols
Augmented Ninth is written A9, 9A: the letter is the quality, the number the size. Chord formulas on this site write the number first, as tonal does.
A compound interval is a simple interval plus an octave, and the two names are used interchangeably in chord symbols: a 9th in a chord is the 2nd of the scale an octave up, an 11th the 4th, a 13th the 6th. The compound name says the note sits above the seventh.
How it sounds
A Augmented Ninth spans 15 semitones: C – D#. It is an octave plus an augmented second, and compound intervals keep the quality of the simple interval inside them while losing much of its edge — the extra octave gives the two notes room to stop interfering with each other.
It measures the same as a minor tenth, and in a dominant context it is heard as a minor third sounding against a major third.
How it is used
This is the Hendrix chord: the ♯9 on a dominant seventh, major and minor thirds colliding on purpose. It is the sound of funk and of hard bop alike.
Learn this properly
Chapter 5: IntervalsCommon questions
- How many semitones is an augmented ninth?
- A Augmented Ninth spans 15 semitones: C – D#. Count the semitones of any interval with the interval calculator.
- What is the Hendrix chord?
- A dominant seventh with a sharp ninth — 7♯9. Purple Haze made it famous, and it works because the ♯9 is enharmonically the minor third rubbing against the chord's major third.
- What is a compound interval?
- Any interval wider than an octave. A Augmented Ninth is an octave plus an augmented second, and it keeps the character of that simple interval in a more open, less congested form.
- How do I play Augmented Ninth?
- On guitar the handiest shape is Next string, B 1 · E 11, read as string and fret; the instrument panel draws it from any starting note with the other shapes. On the piano count 15 semitones up from any key, black keys included. Play the notes together for the harmonic form, one after the other for the melodic form.
- What is the inversion of Augmented Ninth?
- The inversion of Augmented Ninth is the Diminished Seventh: put the lower note an octave higher and the distance that remains is the inversion. The two always add up to an octave, 15 semitones and 9 semitones, and swap their qualities between major and minor, or keep perfect as perfect.