Intervals
Augmented Third
3A · 5 semitones
A third stretched to the width of a perfect fourth, produced by chromatic spelling rather than by design.
Also written A3 · 3A
Augmented Third
3A · 5 semitones
On the piano, from every note
| From | Notes | Play it on your instrument |
|---|---|---|
| C | C – E# | |
| C# | C# – E## | |
| D | D – F## | |
| Eb | Eb – G# | |
| E | E – G## | |
| F | F – A# | |
| F# | F# – A## | |
| G | G – B# | |
| Ab | Ab – C# | |
| A | A – C## | |
| Bb | Bb – D# | |
| B | B – D## |
Tap a key or a fret to hear it.
Read on: number and quality · inversion · compound intervals · consonance and dissonance
Every third
A third can take these qualities, one semitone apart; choose one to see the upper note move and hear the pair.
Understanding Augmented Third
Names and symbols
Augmented Third is written A3, 3A: the letter is the quality, the number the size. Chord formulas on this site write the number first, as tonal does.
Seconds, thirds, sixths and sevenths come in major and minor, a semitone apart, and can be widened to augmented or narrowed to diminished. Inverting one swaps the quality: a major third becomes a minor sixth, a minor second a major seventh.
How it sounds
An augmented third spans 5 semitones: C – E#. It is indistinguishable by ear from a perfect fourth; only the notation, which keeps the two notes on letter names a third apart, tells them apart.
Where it comes from
You will find it in dense chromatic passages and in theoretical keys with many accidentals, where a raised third has to keep its letter name to show which degree it belongs to. It is rare enough that most musicians meet it only in analysis.
Learn this properly
Chapter 5: IntervalsCommon questions
- How many semitones is an Augmented Third?
- Five — C – E# — the same distance as a perfect fourth. Count the semitones of any interval with the interval calculator.
- Is an augmented third the same as a perfect fourth?
- Identical in sound, different in spelling and in function. The augmented third keeps both notes on letter names a third apart.
- Where would I see one written?
- Almost only in heavily chromatic music or in keys with double accidentals, where spelling must follow the harmonic function.
- How do I play Augmented Third?
- On guitar the handiest shape is Next string, B 1 · E 1, read as string and fret; the instrument panel draws it from any starting note with the other shapes. On the piano count 5 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 Third?
- The inversion of Augmented Third is the Diminished Sixth: put the lower note an octave higher and the distance that remains is the inversion. The two always add up to an octave, 5 semitones and 7 semitones, and swap their qualities between major and minor, or keep perfect as perfect.