Intervals
Diminished Second
2d · no semitones
A theoretical interval that spans no distance at all in equal temperament, written across two letter names.
Also written d2 · 2d
Diminished Second
2d · no semitones
On the piano, from every note
| From | Notes | Play it on your instrument |
|---|---|---|
| C | C – Dbb | |
| C# | C# – Db | |
| D | D – Ebb | |
| Eb | Eb – Fbb | |
| E | E – Fb | |
| F | F – Gbb | |
| F# | F# – Gb | |
| G | G – Abb | |
| Ab | Ab – Bbbb | |
| A | A – Bbb | |
| Bb | Bb – Cbb | |
| B | B – Cb |
Tap a key or a fret to hear it.
Read on: number and quality · half steps and whole steps · inversion · compound intervals · consonance and dissonance
Every second
A second can take these qualities, one semitone apart; choose one to see the upper note move and hear the pair.
Understanding Diminished Second
Names and symbols
Diminished Second is written d2, 2d: the letter is the quality, the number the size. Chord formulas on this site write the number first, as tonal does.
A unison is the interval of no distance, and it still has a quality: raise one of the two notes and it is an augmented unison, a chromatic half step that keeps its letter. A diminished second is the same distance written with two letters, C to D♭♭, which almost never happens outside theory exercises.
How it sounds
A diminished second spans 0 semitones: C – Dbb. On a piano the two notes are the same key. It exists on paper because the letters differ — B♯ and C, for instance — and notation tracks function, not just sound.
Where it comes from
You meet it in heavily chromatic writing and in keys with many accidentals, where a leading tone resolves onto a note already spelled as its enharmonic. In historical tunings other than equal temperament it is genuinely audible, and its size is the comma by which those tunings differ.
Learn this properly
Chapter 5: IntervalsCommon questions
- How many semitones is a Diminished Second?
- Zero in equal temperament — C – Dbb are the same pitch, written with different letter names. Count the semitones of any interval with the interval calculator.
- Does the diminished second ever sound?
- In equal temperament, no. In meantone and just tunings it is a small but real interval, which is where the term "diminished second" originally earned its keep.
- Why bother writing one?
- Because the spelling tells a reader which scale degree a note belongs to, and that governs how the passage resolves.
- How do I play Diminished Second?
- On guitar the handiest shape is Next string, G 5 · B 1, read as string and fret; the instrument panel draws it from any starting note with the other shapes. On the piano count no 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 Diminished Second?
- The inversion of Diminished Second is the Augmented Seventh: put the lower note an octave higher and the distance that remains is the inversion. The two always add up to an octave, no semitones and 12 semitones, and swap their qualities between major and minor, or keep perfect as perfect.