Common Tones

Two, one, none

Take the home chord, I. The chords on the 3rd and 6th notes of the scale (iii and vi) share two of its notes, so only one finger moves. IV and V share one note, so two fingers move. ii and vii° share nothing: all three move. Every one of those moves is a half step or a whole step.

Up or down

Lift the notes and you reach vi, IV and ii: the side that leans away from home. Let them sink and you reach iii, V and vii°: the side that pulls back home. The leading tone (the 7th note of the scale) arrives on the way down.

Four ways round the key

Move the roots down a third or up a third and two notes stay each time. Move them up a fourth (round the circle of fifths) or up a fifth and one note stays. All four walks visit every chord in the key, and your hand barely moves. With seventh chords, each walk keeps one more note.

In minor

The relative minor uses the same notes, so the ladder is the same: VI, iv and ii° rise; III, v and VII fall. Harmonic minor raises the 7th note, which makes v a major V and puts a half step on the falling side.

With seventh chords

Add the 7th and every chord shares at least one note with home: iii7 and vi7 share three, IVmaj7 and V7 share two, ii7 and viiø7 share one. The 1–2–3 pattern stays, but the direction flips: vi7 drops the 7th, iii7 lifts the root.

Why the names

The dominant is a fifth above home; the subdominant is the same distance below. The mediant sits halfway up to the dominant, and the submediant halfway down to the subdominant. The relative minor is the submediant chord.

Practise like this

1. Thirds down, one finger at a time.
2. The same seven chords other ways round: thirds up, the circle, fifths up.
3. Out and back from root position. Hold the shared notes down.
4. The same from the 1st and 2nd inversions.
5. Ears only: the quiz above, five a day.
6. Minor, then the next key round the circle.