Chord
A chord is the sound of at least three different tones at once. The most common chord is the triad: a root with two stacked thirds above it. Whether it sounds bright (major) or dark (minor) is decided by the lower third.
How a chord is built
You start with a root and stack two thirds above it, skipping every other tone of the scale. From C this gives C–E–G, the C major triad. The three tones are called root, third and fifth. Stack one more third on top and you get a seventh chord of four tones.
| Triad | Structure | Example on C |
|---|---|---|
| major | major + minor third 4 + 3 semitones | C C–E–G |
| minor | minor + major third 3 + 4 semitones | Cm C–E♭–G |
| diminished | two minor thirds 3 + 3 semitones | C° C–E♭–G♭ |
| augmented | two major thirds 4 + 4 semitones | C+ C–E–G♯ |
In major and minor the outer fifth is perfect, which gives a stable, restful sound. Diminished and augmented chords sound unstable because their fifth is narrowed or widened; they ask for resolution.
Hearing major and minor
The two chords share two of their three tones. Only the third is shifted by a semitone, and that is enough to tip the mood. The article Major and minor: the third as a switch explains why.
Chords in a key
If you build a triad on every degree of a scale using only notes of that scale, you get seven chords that all fit the key. In C major they are C, Dm, Em, F, G, Am and B°. The order major–minor–minor–major–major–minor–diminished holds in every major key. What role each of these chords plays is explained on the page Diatonic chords.
In songbooks, chords appear as symbols above the notes: C is a major triad, Cm a minor triad, C7 a dominant seventh chord. C/E means C major with E in the bass, which is an inversion.
Common mistakes
- Knowing only the symbol: A chord symbol is shorthand. If you know how thirds are stacked, you can work out any chord.
- Taking an inversion for a different chord: A chord keeps its name whichever tone is at the bottom.
- Taking two tones for a chord: A chord has at least three different tones. Two tones make an interval.
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Related terms
TriadMajor triadMinor triadSeventh chordChord inversionDiatonic chordRootThirdCadence
Editor: Maik Krohm · reviewed on 3 October 2026
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