Guide · Guitar theory
Why chords in a key are major or minor
Every chord in a key is built from the key's own notes by stacking every other note of the scale. The scale's mix of whole and The smallest distance in Western music: one fret on the guitar, such as E to F or F to F♯. makes some stacks major, some minor and one A chord with a minor 3rd and a flattened 5th, written °. It sounds tense, and is the vii° chord of a major key.: in any major key I, IV and V are major, ii, iii and vi are minor, and vii° is diminished.
Chords are stacked from the scale
Take a note of the scale, skip one, take the next, skip one, take the next: that is a A three-note chord stacked in 3rds: a root, a 3rd and a 5th. Major, minor, diminished and augmented chords are triads..
The C major scale is C D E F G A B. Starting on C and taking every other note gives C, E and G: the C chord. Starting on D gives D, F and A: Dm. Do it from every note and you have the seven chords of the key, C, Dm, Em, F, G, Am and B°.
This is called stacking thirds, because the distance from each note to the next one you take is a third. The basics page builds these chords one note at a time, with sound.
The size of the thirds decides the quality
A major third (four The smallest distance in Western music: one fret on the guitar, such as E to F or F to F♯.) with a minor third on top makes a major chord; the other way round makes it minor.
In C, C to the next note is 4 half steps and the third to the fifth is 3: major, then minor, which makes a major chord. In Dm the gaps are 3 and 4: minor, then major, which makes it minor. In B° both gaps are 3: two minor thirds, a A chord with a minor 3rd and a flattened 5th, written °. It sounds tense, and is the vii° chord of a major key. chord.
The scale is not even. Most steps are Two half steps, or two frets on the guitar, such as C to D., but two are half steps, E to F and B to C in C major. Wherever a stack crosses one of those half steps, its third gets smaller. That alone decides which chords come out major and which minor.
The pattern in every major key
Every major key has the same pattern of qualities: major, minor, minor, major, major, minor, A chord with a minor 3rd and a flattened 5th, written °. It sounds tense, and is the vii° chord of a major key..
In A chord written by its place in the key: upper case for major (IV), lower case for minor (vi), ° for diminished. that is I ii iii IV V vi vii°. In D major the chords are D, Em, F♯m, G, A, Bm and C♯°: the same pattern from a different starting note. Every major scale has the same steps, so every major key gives the same qualities.
That is what makes chord numbers so useful. If you know a song is I–vi–IV–V, you know the second chord is minor without knowing the key. The Roman numeral guide covers the notation.
The pattern in minor keys
A The minor scale with the same notes as its relative major: in A minor, A B C D E F G. key starts the same chords from the sixth degree, so its pattern is minor, A chord with a minor 3rd and a flattened 5th, written °. It sounds tense, and is the vii° chord of a major key., major, minor, minor, major, major.
A minor uses the notes of C major starting from A, so its chords are Am, B°, C, Dm, Em, F and G, or i ii° III iv v VI VII.
Minor-key songs usually change one of them. Raising the seventh note of the scale, G to G♯ in A minor, turns the weak Em into E, a major V chord that pulls strongly back to Am. That raised note comes from the The natural minor scale with its 7th raised a half step, which makes the V chord major and gives it a strong pull home. scale.
Add a fourth note for seventh chords
Stack one more third and each chord becomes a A triad with one more 3rd on top, the 7th, which makes four notes: G7, Cmaj7 and Am7 are seventh chords., with its own fixed quality in the key.
In C major the seventh chords are Cmaj7, Dm7, Em7, Fmaj7, G7, Am7 and Bm7♭5. Only one of them, the chord on the fifth degree, is a A major chord with a minor 7th added, such as G7. It is the V7 of a key and pulls strongly to the I chord., and that is why G7 sounds like it has to resolve to C.
In A minor the The minor scale with the same notes as its relative major: in A minor, A B C D E F G. sevenths are Am7, Bm7♭5, Cmaj7, Dm7, Em7, Fmaj7 and G7. Seventh chords add colour while keeping the job each chord does in the key; the harmonisation view on the circle lets you switch between A three-note chord stacked in 3rds: a root, a 3rd and a 5th. Major, minor, diminished and augmented chords are triads. and sevenths in any key.