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How to build a chord on the piano

Every basic chord is built in three steps: pick a root, add a third above it, then a fifth. Counting letters gives the note names; counting semitones gives the exact keys, 4 then 7 for a major chord, 3 then 7 for a minor one. Below, you build a few chords yourself, with each key checked as you go.

Root, third, fifth: count the letters

Every basic chord is built the same way, from the bottom up. First pick the root: it is the note that names the chord. Then count note letters upwards, with the root as number 1. On C: C is 1, D is 2, E is 3, F is 4, G is 5. The third is the note on 3, the fifth is the note on 5. That gives C, E and G.

On the keyboard, the letters you skip (here D and F, shown in grey) are the white keys between the chord notes. Listen to the chord appear one layer at a time.

  • Root
  • Third and fifth
  • Skipped letters

← Slide the keyboard to see every key →

  1. Root
  2. + third
  3. + fifth
C alone, then C and E, then C, E and G: a C major chord.

Then check the distances

Counting letters gives the right note names, but not yet the right chord. What decides between major and minor is the exact size of each gap, measured in semitones. A semitone is the step from one key to the very next one, black or white.

  • Major chord: the third is 4 semitones above the root, the fifth 7.
  • Minor chord: the third is 3 semitones above the root, the fifth 7.

Try it on D. Counting letters gives D, F and A. From D to F is only 3 semitones, so D F A is D minor. For D major, the third must be 4 semitones up: raise F by one semitone to F♯. The letter stays F and only gains a sharp, which is why the chord is spelled D F♯ A, not D G♭ A.

← Slide the keyboard to see every key →

D to F: 3 semitones, a minor third. These letters alone give Dm.

The fifth needs a quick check too. It is 7 semitones above the root on every white key but one: B. From B to F is only 6. We come back to that chord at the end.

Build it yourself

Choose a chord, press its root, then its third, then its fifth. Each key is checked by its distance from the root. If you press the wrong one, the message tells you how many semitones you counted and how many the chord needs, so you can correct it by moving one key at a time.

Start with C major and A minor, which use white keys only, then D major, E minor and A major: two of these need a black key for their third.

Your turn

Build these five chords

Start with the root: C.

Step 1 of 3

← Slide the keyboard to see every key →

Two rarer triads, and where to check

Change the fifth instead of the third and you get two more triads. A diminished chord stacks two minor thirds, 3 semitones and 3 more, so its fifth is only 6 semitones above the root: B D F is one. An augmented chord stacks two major thirds, 4 and 4, so its fifth is 8 semitones up: C E G♯.

Both sound less settled than major and minor to most ears, and you will meet them less often. It is enough to recognise them for now.

← Slide the keyboard to see every key →

B D F: from B to F, 6 semitones. Written Bdim or B°.

To check a chord you built, open its sheet: notes, keyboard and sound. Here are the five from the exercise.

  • C: C E G
  • Am: A C E
  • D: D F♯ A
  • Em: E G B
  • A: A C♯ E

For any other chord, the chord dictionary lists the notes of every common chord on all twelve roots.

In short

  1. Count letters from the root: 1, 3 and 5 give the chord’s note names.
  2. Count semitones for the exact keys: 4 + 7 for major, 3 + 7 for minor.
  3. A sharp or flat adjusts a note without changing its letter: D F♯ A, not D G♭ A.