Chord Spelling
Spelling a chord is two independent steps, and almost everyone tries to do them at once. Step one: get the letters, which come from stacking thirds and never change. Step two: apply the key signature, which decides the sharps and flats. Separate them and every chord in every key falls out of the same short procedure.
Practice it: Harmony Drill — spell and hear these chords against the clock.
Step 1: the letters come from thirds
Stack the musical alphabet in thirds — every other letter — and you get one repeating ladder: C E G B D F A, then back to C. Every chord is a consecutive slice of it. Three in a row is a triad, four is a seventh chord.
That's the whole of step one. The musical alphabet covers why this ladder is also where the clef mnemonics come from.
Step 2: the key signature decides the accidentals
In C major there are no sharps or flats, so the letters are the chords. That's the only reason C looks special — it isn't simpler, it just has an empty step two.
Every chord in C major
| Degree | Letters | Chord | Add a 4th | Seventh chord |
|---|---|---|---|---|
| I | C E G | C major | C E G B | Cmaj7 |
| ii | D F A | D minor | D F A C | Dm7 |
| iii | E G B | E minor | E G B D | Em7 |
| IV | F A C | F major | F A C E | Fmaj7 |
| V | G B D | G major | G B D F | G7 |
| vi | A C E | A minor | A C E G | Am7 |
| vii° | B D F | B diminished | B D F A | Bm7♭5 |
Why those qualities, and not others
Nobody decided that D F A should be minor. It falls out of where the half steps sit. A major scale has exactly two, between degrees 3–4 and 7–8 — in C, that's E–F and B–C:
A triad is major when its lower third spans four semitones and minor when it spans three. C to E steps over no half step and comes out major; D to F crosses E–F and comes out minor. Run that across all seven and you get a fixed pattern:
I ii iii IV V vi vii°
That pattern is a property of the major scale, not of C. It is identical in every major key — which is what makes the next part work.
Deriving another key: A major
Same two steps. Nothing new to memorise.
a. Spell the scale
A major scale, built with the usual whole/half pattern (W W H W W W H): A B C♯ D E F♯ G♯. Its key signature is three sharps — F♯, C♯, G♯ — which is just the first three of the order of sharps, F C G.
b. Read the same ladder, starting on A
The thirds ladder doesn't change; you just enter it at a different point: A C E G B D F. Those are the letters, and they're fixed before you think about a single accidental.
c. Apply the key signature
Every F, C and G in the key is sharp. So A C E G becomes A C♯ E G♯, and B D F becomes B D F♯. The letters were already right; the signature just coloured them in.
| Degree | Letters | Chord | Add a 4th | Seventh chord |
|---|---|---|---|---|
| I | A C♯ E | A major | A C♯ E G♯ | Amaj7 |
| ii | B D F♯ | B minor | B D F♯ A | Bm7 |
| iii | C♯ E G♯ | C♯ minor | C♯ E G♯ B | C♯m7 |
| IV | D F♯ A | D major | D F♯ A C♯ | Dmaj7 |
| V | E G♯ B | E major | E G♯ B D | E7 |
| vi | F♯ A C♯ | F♯ minor | F♯ A C♯ E | F♯m7 |
| vii° | G♯ B D | G♯ diminished | G♯ B D F♯ | G♯m7♭5 |
Compare it to the C table: same degrees, same qualities, same order — major, minor, minor, major, major, minor, diminished. Only the letters and accidentals moved. That's the whole trick. There is no separate body of knowledge called "chords in A major."
The procedure, for any key
- Start on the root and take every other letter: root, skip, skip — three or four of them.
- Apply the key signature to whichever of those letters it touches.
- Sanity-check against the pattern. Degrees I, IV and V are major; ii, iii and vi are minor; vii° is diminished. If your spelling disagrees, one of the first two steps went wrong.
Worth noticing: step 3 is a genuine check, not decoration. Spell the chord on D in A major as D F A and the pattern says IV should be major — that flags the missing sharp before you play a wrong note.
Beyond the seventh: 9ths, 11ths and 13ths
Jazz chord symbols look like a separate vocabulary, and they aren't. A ninth chord is a seventh chord with one more rung of the same ladder. An eleventh adds the next. A thirteenth adds the one after that — at which point you have used all seven letters and the ladder closes on itself. There is nothing above a 13th, because there's nothing left to add.
The odd numbers are the giveaway. 1, 3, 5, 7, 9, 11, 13 is just "every other letter" counted past the octave: the 9th is the 2nd an octave up, the 11th is the 4th, the 13th is the 6th. So the extensions are precisely the three letters a seventh chord left out.
The letters, for every chord in C major
Keep walking the ladder from each root. That's the entire method:
| Chord | 1 3 5 7 | 9 | 11 | 13 | Full stack |
|---|---|---|---|---|---|
| Cmaj7 | C E G B | D | F | A | C E G B D F A |
| Dm7 | D F A C | E | G | B | D F A C E G B |
| Em7 | E G B D | F | A | C | E G B D F A C |
| Fmaj7 | F A C E | G | B | D | F A C E G B D |
| G7 | G B D F | A | C | E | G B D F A C E |
| Am7 | A C E G | B | D | F | A C E G B D F |
| Bm7♭5 | B D F A | C | E | G | B D F A C E G |
Every row is the same seven letters starting one rung later. Once that's visible, "what's the 11th of Am7" stops being a lookup and becomes counting: A C E G, then B, D.
Which extensions actually get played
Having a letter available isn't the same as it sounding good, and this is where the diatonic picture gets honest. Two things constrain real usage:
- The natural 11 clashes over major and dominant chords. F against a C major chord is a half step above E, its third — so Cmaj13 and G13 are normally played without the 11. On minor chords there's no such clash, which is why Dm11 and Am11 are common and Cmaj11 essentially isn't.
- iii and vii° carry a ♭9. Walk the ladder from E and the 9th is F — a half step above the root. Same from B, where the 9th is C. That flat ninth is why those two chords are rarely extended, and why the iii chord tends to appear as a plain Em7.
One that goes the other way: the 11th of Fmaj7 is B, a ♯11 against F — not a clash but the Lydian colour, and a large part of why the IV chord sounds the way it does in jazz.
In practice nobody plays all seven notes. Pianists typically keep the third and seventh — the two notes that define the quality — plus whichever extensions are wanted, and drop the fifth and often the root, since the bass has it covered.
In any other key
Unchanged: walk the ladder from the root for as many rungs as the symbol asks, then apply the key signature. In A major, the 9th of Bm7 is C♯ — the ladder gives C, the three sharps make it C♯. Step one, then step two, exactly as before.
Why this matters when you're reading
On the page, a root-position chord is a stack of noteheads all on lines or all on spaces — because thirds are exactly one staff position apart. You don't read three notes and assemble a chord; you see the shape, take the bottom letter, and the rest follows from the ladder.
That's the real payoff. Chord spelling isn't trivia — it's what lets you take in three or four notes as one object instead of decoding each one, which is most of what separates a fluent sight-reader from a slow one.
Practise it free
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