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