dispelledChords
A chord is three or more notes played simultaneously to create harmony. Understanding chord construction — how chords are built from intervals — lets you figure out any chord by ear or analysis, and tells you what voicings and extensions will work in a given context. The chord symbol is a compact description of its construction; being able to decode and rebuild any symbol is a fundamental skill.
Intervals — The Building Blocks
| Interval name | Abbreviation | Semitones | Example from C |
|---|---|---|---|
| Minor 2nd (half step) | m2 | 1 | C → D♭ |
| Major 2nd (whole step) | M2 | 2 | C → D |
| Minor 3rd | m3 | 3 | C → E♭ |
| Major 3rd | M3 | 4 | C → E |
| Perfect 4th | P4 | 5 | C → F |
| Tritone (aug 4th / dim 5th) | TT | 6 | C → F#/G♭ |
| Perfect 5th | P5 | 7 | C → G |
| Minor 6th (aug 5th) | m6 | 8 | C → A♭/G# |
| Major 6th | M6 | 9 | C → A |
| Minor 7th | m7 | 10 | C → B♭ |
| Major 7th | M7 | 11 | C → B |
| Octave | P8 | 12 | C → C |
Triads
Root, third, and fifth — the basic building block:
| Triad type | Construction | Semitones | Example (C) | Sound |
|---|---|---|---|---|
| Major | Root + M3 + P5 | 4 + 3 | C E G | Bright, resolved, stable |
| Minor | Root + m3 + P5 | 3 + 4 | C E♭ G | Darker, introspective, stable |
| Diminished | Root + m3 + d5 | 3 + 3 | C E♭ G♭ | Tense, unstable — wants to resolve |
| Augmented | Root + M3 + A5 | 4 + 4 | C E G# | Ambiguous, floating — symmetrical, no clear root |
| Suspended 4th | Root + P4 + P5 | 5 + 2 | C F G | Unresolved, ambiguous (no 3rd) |
| Suspended 2nd | Root + M2 + P5 | 2 + 5 | C D G | Open, floating (no 3rd) |
Seventh Chords
Add a fourth note (a seventh above the root) for the harmonic richness that jazz and modern harmony rely on:
| Chord type | Symbol | Construction | Example (C) | Typical function |
|---|---|---|---|---|
| Major 7th | maj7, Δ7 | M3 + P5 + M7 | C E G B | Tonic — stable, lush |
| Dominant 7th | 7 | M3 + P5 + m7 | C E G B♭ | Dominant — strong pull to resolution (tritone in 3rd and 7th) |
| Minor 7th | m7, −7 | m3 + P5 + m7 | C E♭ G B♭ | Pre-dominant (ii chord) or tonic (vi chord) |
| Minor-major 7th | m(maj7), mΔ7 | m3 + P5 + M7 | C E♭ G B | Tonic in minor key (Im with raised 7th) — exotic, unstable |
| Half-diminished | ø7, m7♭5 | m3 + d5 + m7 | C E♭ G♭ B♭ | ii° in minor key — pre-dominant |
| Diminished 7th | °7, dim7 | m3 + d5 + d7 | C E♭ G♭ B♭♭(A) | Diminished — symmetric, can resolve to any chord a half step above any note |
| Major 6th | 6, maj6 | M3 + P5 + M6 | C E G A | Tonic substitute in jazz (same notes as Am7 in root position) |
| Minor 6th | m6 | m3 + P5 + M6 | C E♭ G A | Minor tonic substitute |
Extended Chords
Continue stacking thirds above the seventh to get 9ths, 11ths, and 13ths. These numbers refer to the same intervals as the 2nd, 4th, and 6th, raised by one octave:
9th = same pitch class as 2nd (M2 or m2 up an octave from root) 11th = same pitch class as 4th (P4 or #4 up an octave) 13th = same pitch class as 6th (M6 or m6 up an octave) Common extended chords: Cmaj9: C E G B D (maj7 + major 9th) C9: C E G B♭ D (dom7 + major 9th) Cm9: C E♭ G B♭ D (m7 + major 9th) C7#11: C E G B♭ F# (Lydian dominant — tritone against root) C13: C E G B♭ D A (dom7 + 9th + 13th — leave out 11th usually) Cmaj13: C E G B D F# A (all seven notes — rarely voiced complete)
Voicing: Which Notes to Play
In practice, extended chord voicings leave some notes out. The guiding principle is that the 3rd and 7th define the chord's identity:
| Note | Include? | Why |
|---|---|---|
| Root | Sometimes (often bass player's job) | Bass covers it — rootless voicings are common in jazz piano |
| 3rd | Always | Defines major vs minor quality |
| 5th | Often omit | Least interesting, adds little colour (unless altered) |
| 7th | Always (in jazz) | Defines dominant vs major vs minor character |
| 9th, 11th, 13th | Selective | Colour and context — choose what serves the melody and voice leading |
Inversions
C major triad: Root position: C E G (root in bass) 1st inversion: E G C (3rd in bass) — written C/E 2nd inversion: G C E (5th in bass) — written C/G Seventh chord inversions: Cmaj7 root: C E G B Cmaj7 1st: E G B C (3rd in bass) — C/E Cmaj7 2nd: G B C E (5th in bass) — C/G Cmaj7 3rd: B C E G (7th in bass) — C/B
Inversions change the weight and stability. Second inversion (6/4 chord) sounds unstable over a non-root bass note — useful as a suspension before cadential resolution. Slash chords in pop (G/B, D/F#) specify the bass note of an inverted chord.
Chord Symbol Decoding
| Symbol | Meaning | Notes (from C) |
|---|---|---|
| C | C major triad | C E G |
| Cm | C minor triad | C E♭ G |
| C7 | C dominant 7th | C E G B♭ |
| Cmaj7 or CΔ | C major 7th | C E G B |
| Cm7 | C minor 7th | C E♭ G B♭ |
| C7sus4 | C dominant, suspended 4th | C F G B♭ |
| C7♭9 | C dominant, flat 9 | C E G B♭ D♭ |
| C7#9 | C dominant, sharp 9 ("Hendrix chord") | C E G B♭ D# |
| Cadd9 | C major triad + 9th (no 7th) | C D E G |
| C/E | C major in 1st inversion (E in bass) | E (bass) C E G |
References
- Levine — The Jazz Theory Book
- Rawlins & Bahha — Jazzology
- musictheory.net — Chord Building ↗