1. What Makes a Chord?

A chord is three or more different pitches sounding simultaneously. Two notes form an interval; three or more form a chord. While this seems simple, the variety of possible combinations creates thousands of distinct chord types, each with unique sonic character.

Chords are built from intervals stacked above a root note. The specific intervals determine the chord's quality—major, minor, diminished, augmented, and their many extensions and alterations.

Our Interval Calculator helps you understand the building blocks from which all chords are constructed.

2. Basic Triads

Triads are three-note chords built by stacking thirds. They form the foundation of Western harmony and the basis from which all other chords are understood.

Major Triad

Root + Major 3rd + Perfect 5th (0-4-7 semitones). Example: C-E-G. Character: stable, bright, happy. Symbol: C or Cmaj.

Minor Triad

Root + Minor 3rd + Perfect 5th (0-3-7 semitones). Example: C-E♭-G. Character: stable but darker, sad. Symbol: Cm or Cmin or C-.

Diminished Triad

Root + Minor 3rd + Diminished 5th (0-3-6 semitones). Example: C-E♭-G♭. Character: tense, unstable, wants to resolve. Symbol: Cdim or C°.

Augmented Triad

Root + Major 3rd + Augmented 5th (0-4-8 semitones). Example: C-E-G#. Character: mysterious, unresolved, dreamy. Symbol: Caug or C+.

3. Seventh Chords

Adding a seventh above the root creates seventh chords—four-note structures that add complexity and direction to harmony. Sevenths are essential in jazz but appear across all genres.

Major Seventh (maj7)

Major triad + Major 7th (0-4-7-11). Example: C-E-G-B. Character: lush, sophisticated, jazzy. The major 7th interval creates a gentle dissonance that sounds modern and beautiful.

Dominant Seventh (7)

Major triad + Minor 7th (0-4-7-10). Example: C-E-G-B♭. Character: bluesy, wants to resolve down a fifth. The tritone between the 3rd and ♭7th creates tension seeking resolution.

Minor Seventh (m7)

Minor triad + Minor 7th (0-3-7-10). Example: C-E♭-G-B♭. Character: smooth, mellow, the default jazz minor chord. Very stable and usable.

Half-Diminished (m7♭5)

Diminished triad + Minor 7th (0-3-6-10). Example: C-E♭-G♭-B♭. Symbol: Cm7♭5 or Cø. Common as the ii chord in minor keys.

Diminished Seventh (dim7)

Diminished triad + Diminished 7th (0-3-6-9). Example: C-E♭-G♭-B𝄫. All minor thirds—symmetrical and ambiguous. Any note can sound like the root.

4. Extended Chords

Extended chords add the 9th, 11th, and 13th above the seventh. These stack additional thirds to create rich, complex harmonies favored in jazz, R&B, and neo-soul.

Ninth Chords

Seventh chord + 9th. Example: C9 = C-E-G-B♭-D. The 9th is the 2nd degree up an octave. Major 9 (Cmaj9) uses major 7th; dominant 9 (C9) uses minor 7th.

Eleventh Chords

Ninth chord + 11th. The 11th (perfect 4th up an octave) often conflicts with the major 3rd, so the 3rd is frequently omitted or the 11th is raised (#11). Minor 11 chords are more common than major 11.

Thirteenth Chords

Eleventh chord + 13th. Example: C13 contains (theoretically) C-E-G-B♭-D-F-A. In practice, notes are omitted—the 5th and often 9th or 11th. The 13th (major 6th up an octave) adds brightness.

5. Inversions and Voicings

Inversions place a note other than the root in the bass. The same notes rearranged create different colors and voice-leading possibilities.

Triad Inversions

Root position: root in bass (C-E-G with C lowest). First inversion: 3rd in bass (E-G-C). Second inversion: 5th in bass (G-C-E). Notation: C/E means C chord with E in bass.

Seventh Chord Inversions

Four notes means four possible inversions. Third inversion (7th in bass) creates strong downward pull—B♭-C-E-G wants to resolve down to A or F.

Voicing vs. Inversion

Voicing refers to the spacing and arrangement of chord tones across registers, regardless of which note is lowest. Close voicing keeps notes within an octave; open voicing spreads them further apart. Same chord, very different sounds.

6. Chord Identification Process

When you encounter unknown notes and need to identify the chord, follow this systematic approach.

Step 1: Reduce to Pitch Classes

Ignore octaves and doublings. C3-E4-G4-C5 reduces to C-E-G. List unique note names.

Step 2: Test Each Note as Root

Calculate intervals from each note to every other note. The arrangement that matches known chord formulas reveals the chord. C-E-G: from C, intervals are M3 and P5 = major triad. If you tested from E first: E to G is m3, E to C is m6—doesn't match standard triads, so E isn't the root.

Step 3: Consider Context

The bass note and musical context matter. C-E-G with E in bass is typically called C/E (C first inversion), but in certain contexts might be analyzed differently. The chord's function in the progression helps determine the best name.

7. Altered and Suspended Chords

Alterations modify chord tones chromatically. Suspensions replace the third. These variations expand the harmonic palette considerably.

Suspended Chords

Sus4: Replace 3rd with 4th (C-F-G). Sus2: Replace 3rd with 2nd (C-D-G). Neither major nor minor—they suspend that determination, creating expectation of resolution.

Altered Dominants

Dominant chords with chromatically altered 5ths and/or 9ths. C7(♭9), C7(#9), C7(♭5), C7(#5), C7alt (multiple alterations). These increase tension and facilitate chromatic voice leading in jazz.

Added Tone Chords

Add9 (Cadd9) adds the 9th without the 7th: C-E-G-D. Different from C9 which requires the 7th. Add6 similarly adds the 6th: C-E-G-A (sometimes called C6).

8. Context-Based Naming

The same notes can have different names depending on musical context. Understanding this flexibility prevents confusion and aids communication.

Enharmonic Equivalents

C-E-G# could be C augmented or A♭ augmented with C in bass. Both names describe the same sound. Context—what chords come before and after, what key you're in—determines the correct name.

Slash Chords vs. Inversions

C/E (C with E in bass) is a first inversion C. But C/B♭ puts a non-chord-tone in bass—this isn't really an inversion but a polychord or bass-melody combination. The distinction matters for analysis.

Functional Names

In Roman numeral analysis, chords are named by function: I, IV, V, ii, etc. A chord's function may be clearer than its absolute name. "The V7 chord" tells us its role; "G7 in C major" tells us the specific notes.

Chord identification combines pattern recognition, interval knowledge, and contextual understanding. With practice, identifying chords becomes intuitive—you'll hear "that's a maj7 voicing" before consciously calculating the intervals. This skill accelerates learning songs, analyzing arrangements, and creating your own harmonic progressions.