Circle of Thirds
The Circle of Thirds organizes the 12 chromatic notes by major and minor third relationships — the building blocks of chord construction and chromatic mediant motion.
Outer ring = major thirds (4 semitones) · Inner = minor thirds (3 semitones)
Click any note on the circle to explore its third relationships.
While the Circle of Fifths shows key relationships, the Circle of Thirds groups notes that are a major third (4 semitones) or minor third (3 semitones) apart. These are the intervals that build triads — a root, a third, and a fifth. Chromatic mediants (chords related by thirds) create lush, unexpected harmonic color in film scores and jazz.
Circle of Thirds
Circle of Thirds arranges chords by third relationships rather than fifths, which shows a different set of harmonic connections that the circle of fifths hides.
How to use it
- Click a chord on the circle.
- Read the chords a third away in each direction.
- Compare against fifth relationships to see which notes are shared.
Why thirds reveal something fifths do not
Chords a third apart share two of their three notes. C major is C, E and G; A minor is A, C and E. Two notes in common means one can substitute for the other and the harmony barely shifts, which is the basis of most chord substitution.
The circle of fifths shows which keys are related. The circle of thirds shows which chords can stand in for each other inside a key, which is why it is more useful for reharmonisation than for modulation.
When it helps
- Finding a substitute chord that keeps the melody working.
- Understanding why the relative minor sounds like the major's shadow.
- Reharmonising a progression without changing the tune.
- Seeing which chords share notes at a glance.
Common mistakes
- Treating substitution as always safe. Two shared notes out of three still changes the bass and the function.
- Confusing this with the circle of fifths, which answers a different question.
