Chords
Chord types, heard and tuned
Fourteen chords, each with its notes, its formula and its symbol. Play any of them on any root, together or a note at a time, and hear how pure tuning moves each tone.
| Chord | Notes from the root | In C | Symbol |
|---|---|---|---|
| Major chord | 1 3 5 | C E G | C |
| Minor chord | 1 ♭3 5 | C E♭ G | Cm |
| Diminished chord | 1 ♭3 ♭5 | C E♭ G♭ | Cdim |
| Augmented chord | 1 3 ♯5 | C E G♯ | Caug |
| Sus2 chord | 1 2 5 | C D G | Csus2 |
| Sus4 chord | 1 4 5 | C F G | Csus4 |
| Major 7th chord | 1 3 5 7 | C E G B | Cmaj7 |
| Minor 7th chord | 1 ♭3 5 ♭7 | C E♭ G B♭ | Cm7 |
| Dominant 7th chord | 1 3 5 ♭7 | C E G B♭ | C7 |
| Diminished 7th chord | 1 ♭3 ♭5 𝄫7 | C E♭ G♭ B𝄫 | Cdim7 |
| Half-diminished chord | 1 ♭3 ♭5 ♭7 | C E♭ G♭ B♭ | Cm7♭5 |
| Major 6th chord | 1 3 5 6 | C E G A | C6 |
| Minor 6th chord | 1 ♭3 5 6 | C E♭ G A | Cm6 |
| Add9 chord | 1 3 5 9 | C E G D | Cadd9 |
How chords are built from thirds
Most chords in Western harmony are stacks of thirds. A major third is 4 semitones, a minor third 3. Put a major third on a root and a minor third on top and you have a major chord; the other way up, a minor chord. Two minor thirds make a diminished chord, two major thirds an augmented one. Add one more third on top and you have a seventh chord: dominant, major, minor, half-diminished or diminished.
A formula counts up from the root along its major scale: 3 is the major third, ♭3 the minor third, 5 the fifth, ♭5 and ♯5 the fifth lowered or raised a semitone. Some chords step outside the stack. Sus chords swap the third for a 2 or a 4, sixth chords add a 6, and add9 adds the ninth, the second an octave up, with no seventh.
Pure tuning, and why a choir's chord rings
A piano splits the octave into 12 equal semitones, so it plays in every key, but most of its intervals sit a little off the simple ratios that voices settle into. Pure tuning, also called just intonation, uses those ratios: a fifth of 3:2, a major third of 5:4, a minor third of 6:5. Each chord's card shows how far pure tuning moves every tone from the piano's pitch, in cents (a cent is a hundredth of a semitone).
When a chord is tuned pure, its notes' overtones line up and the slow wobble between them, called beating, stops. Singers call it locking, or ringing: the chord sounds steadier and fuller. The thirds, sixths and sevenths move most: a major third 13.7 cents lower than the piano's, a minor third 15.6 higher, the barbershop seventh 31.2 lower. Fifths hardly move at all, 2.0 cents.
Reading chord symbols
The symbol goes after the root. C alone is C major, Cm is C minor, Cdim or C° diminished, Caug or C+ augmented. A plain 7 means the dominant 7th, so C7 is C, E, G and B♭. A major 7th needs maj7, M7 or Δ: Cmaj7 is C, E, G and B. Cm7♭5 and Cø7 both mean half-diminished, and Cdim7 and C°7 both mean diminished 7th.
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Questions
How many types of chords are there?
There's no fixed number, since any set of notes can be given a name, but most music leans on a handful. The four triads (major, minor, diminished and augmented), the two sus chords, the five common sevenths, the two sixth chords and add9 cover a great deal of it: those are the fourteen here.
What is the difference between a triad and a seventh chord?
A triad has three notes, a seventh chord four. The seventh chord is a triad with one more third on top, which lands a seventh above the root.
What is just intonation?
Tuning by simple whole-number ratios, so that a chord's overtones line up and it stops beating. A piano can't do it in every key, because its notes are fixed. Voices, strings and trombones can, adjusting each note to the chord it's in.
Why does an a cappella group sound different from a piano?
Partly because of tuning: unaccompanied singers can tune each chord pure, while a piano is tuned in equal steps. Partly it's the sound itself. Voices hold their notes steadily instead of fading, so there's time to hear a chord lock.
Which chord types should I learn first?
Major and minor, since so much music is built from them. Then the dominant 7th, the chord that leads home, then the other sevenths, the sus chords and the rest.
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