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Chord identifier: name a chord from its notes
Press the notes you have on the keyboard. The identifier names the chord — or every chord those notes could be — with the inversion, the correct spelling and a plain explanation of why each name fits. Add a key to see the Roman numeral.
Chord identifier
Try it
Identify a chord
Tap three or more keys. The lowest key is taken as the bass unless you choose another.
None yet.
Press at least three keys, or pick an example. The answer appears here, with every reasonable name for the notes and why each one fits.
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How a chord is identified
A chord is named after its root, not its lowest note. To find the root, stack the notes in thirds until they form a neat pile; the note at the bottom of the pile is the root, and the intervals above it give the chord’s quality. The identifier does the same thing exhaustively: it tries every note you pressed as the root, against every chord type Tomus knows — triads, seventh chords, suspended, sixth and add9 chords — and keeps the ones that account for the notes.
A chord with a note missing can still be recognised. The fifth is the note most often left out, because it adds the least colour: C – E – B♭ is C7 without its fifth, and the tool says so rather than guessing at something more exotic.
Why the bass note matters
The same three notes stacked in a different order are still the same chord, but the note at the bottom changes how it sounds and how it is written. Root position has the root in the bass; a first inversion has the third; a second inversion the fifth; a seventh chord can also stand on its seventh, a third inversion. Chord symbols show this with a slash, chord over bass note.
| Notes, lowest first | Chord | Position |
|---|---|---|
| C – E – G | C | Root position |
| E – G – C | C/E | First inversion |
| G – C – E | C/G | Second inversion |
| B – D – F – G | G7/B | First inversion |
The tool takes the lowest key you press as the bass. You can choose another bass note instead, or ignore the bass and treat the notes as an unordered set. Chord inversions explains why composers choose one position over another.
Why the same notes can have more than one name
Some sets of notes are genuinely two chords. Which one they are depends on the bass and on what is going on around them, so the tool shows both rather than picking one at random:
| Notes | Can be read as |
|---|---|
| C – E – G – A | Am7 (A – C – E – G) or C6 (C – E – G – A) |
| C – D – G | Gsus4 (G – C – D) or Csus2 (C – D – G) |
With a bass note the choice usually becomes clear: with C at the bottom, C – E – G – A is C6; with A at the bottom it is Am7. Two chord types go further. An augmented triad divides the octave into three equal major thirds, and a diminished seventh into four equal minor thirds, so no bass note can show which note is the root: C – E – G♯ reads equally well as Caug, A♭aug, Eaug. Only the spelling, or the key, decides.
Spelling: G♯ or A♭?
A piano key does not know its name. The black key between G and A is G♯ in an E major chord and A♭ in an F minor chord, and the difference is not pedantry: a chord’s notes are spelled by interval from its root, so every third is some kind of third on the page. That is why an augmented triad on E is spelled E – G♯ – B♯, with a B♯ where you pressed the key called C. The identifier spells each reading the way that chord is written, and you can tap a black-key note to say how you spell it — a reading that agrees with your spelling is then preferred. Enharmonic notes covers the idea from the beginning.
What a key adds
Choosing a key never changes the notes, but it changes what the chord means. In C major:
| Notes | Chord | In C major |
|---|---|---|
| G – B – D – F | G7 | V7 — dominant function, in the key |
| E – G♯ – B – D | E7 | V7/vi — a secondary dominant, pointing at vi |
| A♭ – C – E♭ | A♭ | ♭VI — borrowed from C minor |
A key is also evidence. When two readings fit the notes equally, the one that belongs to the key is listed first: in D minor, C♯ – E – G – B♭ is C♯dim7 (vii°7), the leading-tone chord, rather than any of the other three diminished sevenths with the same keys. Roman numerals, secondary dominants and borrowed chords explain the labels.
What it does not do
One chord on its own cannot prove its function — only a progression can — so a Roman numeral here says what the chord can be in the key. To read a whole progression, paste it into the chord progression analyzer. The identifier also leaves out extended and altered jazz chords (ninths, elevenths, thirteenths, ♭9s) and rootless voicings for now: given notes like those, it reports the closest chord it knows and says what is left over. To go the other way — from a chord name to its notes — use the chord explorer, and to move named chords into another key, the chord transposer.