Root motion is the movement from one chord's root to another chord's root.
To demonstrate root motion, we will use a I and a vi chord in C Major.
The root of the I chord (a C major triad) is C.
The root of the vi chord (an A minor triad) is A.
Therefore, the root motion between I and vi (C to A) is down a third.
Due to interval inversion, the root motion could also be classified as up a sixth.
Let's try another example: a IV chord going to V.
The root of the first chord (an F major triad) is F.
The root of the second chord (a G major triad) is G.
Therefore, the root motion of these two chords is up a second or down a seventh.
A circle progression occurs when root motion is equal to up a fourth or down a fifth.
Both I->IV and ii->V are circle progressions.
iii->vi and IV->vii
o are also circle progressions.
Let's work out all possible circle progressions for a major scale, starting at I.
• I progresses to IV, which progresses to vii
o progresses to iii and then to vi.
vi progresses to ii and then to V and finally, to I.
Next, we will work out all possible circle progressions for a minor scale.
i progresses to IV and then to VII (not vii
VII progresses to III and then VI.
VI progresses to iiº, V (not v), and finally i.
This chart displays the circle progressions for both major and minor scales.