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Chords

Notes stacked in thirds — quality, inversions and how chords sit in a key.

Last reviewed September 1, 2026

A chord is three or more notes sounding together. In the tradition most Western music comes from, they are built by stacking thirds.

Triads

Take a note, add the note a third above, then another third above that. Three notes: root, third, fifth. That is a triad, and it accounts for the overwhelming majority of chords you will meet.

Which kind of third you stack decides the quality:

Chord	Lower third	Upper third
Major	major	minor
Minor	minor	major
Diminished	minor	minor
Augmented	major	major

Major vs minor chords unpacks the first two, which are the ones you will use constantly.

Inversions

The same three notes can be stacked in any vertical order. C–E–G, E–G–C and G–C–E are all C major — but they sit differently, move differently and sound different in context. Chord inversions covers what changes and what doesn't.

Beyond triads

Seventh chords add a fourth note and are the standard vocabulary of jazz and pop harmony. Suspended chords replace the third, so they are neither major nor minor. Chord symbols explains how all of this is written on a lead sheet.

Chords belong to keys

A chord rarely appears alone. Build a triad on each degree of a major scale and you get the seven chords that sound native to that key, in a fixed pattern of qualities. That pattern is why so many songs share the same chord shapes in different keys.

What those chords then do — how they group by function, how they form progressions, how they end phrases — is harmony.

Applying it

Once triads and sevenths are familiar, how to learn music theory covers what order to take the rest in, and the chord progression analyzer will name the chords and key of anything you paste into it.