What Is a Chord in Music? How Three Notes Become One Sound
A chord is three or more different notes sounding at the same time, heard as a single sound rather than as separate notes. The most common chord is the triad: three notes stacked a third apart, called the root, the third and the fifth. C major, for example, is C, E and G played together.
What makes three notes a chord?
Three notes become a chord when they are heard together as one thing. Play C, E and G at once and most listeners hear one bright sound named after C, not three notes competing for attention.
Part of the reason is physical. Every note already contains fainter higher tones, its harmonics. In the harmonic series over a low C, harmonics 4, 5 and 6 are C, E and G. A C major chord repeats notes the root’s own sound already contains, so the ear has an easy time fusing them. The harmonic series lesson shows where those notes come from.
The other part is habit. Western music has used these note combinations as single units for centuries, and listeners learn to hear them that way.
How do you build a chord?
You build a triad by stacking two thirds on a starting note. Counting in semitones, the distance from one key to the very next on a keyboard, black or white:
- Pick the root. It names the chord. Take C.
- Add the third. Count 4 semitones up for a major chord (C to E), or 3 for a minor chord (C to E♭).
- Add the fifth. Count 7 semitones up from the root (C to G).
- Play all three together. C–E–G is C major. C–E♭–G is C minor.
On a guitar, the open C major chord frets the fifth string at fret 3, the fourth string at fret 2 and the second string at fret 1, and leaves the third and first strings open. From low to high that sounds C, E, G, C, E: still only three different notes, with C and E doubled.
The major chord lesson drills this recipe from all twelve roots.
What are the four kinds of triad?
There are four triads, and they differ only in the size of the two thirds stacked on the root.
| Triad | Thirds, bottom to top | Semitones above the root | On C | Symbol |
|---|---|---|---|---|
| Major | major + minor | 4 and 7 | C E G | C |
| Minor | minor + major | 3 and 7 | C E♭ G | Cm |
| Diminished | minor + minor | 3 and 6 | C E♭ G♭ | Cdim or C° |
| Augmented | major + major | 4 and 8 | C E G♯ | Caug or C+ |
Major and minor are stable and make up most of the chords in most songs. The difference between them is one semitone in the third, which the article Major vs Minor: One Note Apart explains. Diminished and augmented sound unstable and usually lead somewhere else; the diminished and augmented chords lesson builds both.
Does the order of the notes matter?
The order of the notes does not change which chord it is. C–E–G, E–G–C and G–C–E are all C major. What changes is the voicing, how the notes are spread out, and the lowest note decides the inversion. With C in the bass the chord is in root position; with E or G in the bass it is inverted, written C/E or C/G. The inversions lesson trains you to tell them apart.
Doubling a note does not make a new chord either. The guitar C chord above has five notes and is still a three-note chord.
Do the notes have to be played at the same time?
No. A chord played one note after another is an arpeggio, or a broken chord, and the ear still hears the harmony. Guitar fingerpicking and many piano accompaniments work this way. What makes it a chord is the set of notes, not the moment they start.
Is two notes a chord?
Two notes played together are usually called an interval, not a chord, because a chord needs at least three different notes. The common exception is the guitarist’s power chord: a root and a fifth, such as C and G, written C5. Everyone calls it a chord, and it is useful precisely because it has no third, so it is neither major nor minor.
What about chords with four or more notes?
Stack another third on a triad and you get a seventh chord, with four different notes:
- C7 (dominant seventh): C, E, G, B♭.
- Cmaj7 (major seventh): C, E, G, B.
- Cm7 (minor seventh): C, E♭, G, B♭.
Keep stacking thirds and you reach ninths, elevenths and thirteenths, the extended chords common in jazz. They are still built by the same move: one more third on top.
How do you read a chord symbol?
A chord symbol names the root with a capital letter and adds the quality after it. A letter alone means major (G), a small m means minor (Gm), and a number adds a note (G7). A slash names the bass note (G/B is G major with B in the bass).
A chord symbol says which notes to play, not how to arrange them. The lesson on chord symbols covers what a symbol leaves to the player.
Where do the chords of a song come from?
Most songs take their chords from one key. Stack thirds on each note of a major scale and seven chords come out, in a fixed pattern of major, minor and diminished. The harmonic field lesson builds all seven, and What Is a Chord Progression? shows how songs move between them.
Try it
Build chords before you read more about them. The building chords exercise names a chord and asks you to play it on your own instrument, starting with major and minor triads and moving on to all four qualities and their inversions.