The harmonic field figure
A scale on one wheel, home on top, and the chord on every degree built in front of you — its notes marked one by one, the rest closed, the chord extracted — with a row of small wheels beneath, one a degree, each in its own frame.
Stack thirds on every note of a scale and you get the scale's chords — its harmonic field. This figure builds them in front of you. Tap a size, a scale or one of the small wheels, and the text follows.
The chords of a scale
The big wheel is the scale, home on top, its notes named round the rim. The row beneath is the chord on each degree, every small wheel in its own frame with its root on top — so the row reads as shapes: three of one picture, three of another, one odd. Left alone, the figure builds each chord in turn: its notes marked one by one on the big wheel, the rest closed, the chord extracted in its own colors, then the scale back.
Holding one
Tap a small wheel and that chord is built once and held, and you hear it. Tap it again and the cycle goes on.
Seventh chords
Four notes stacked instead of three. The row is a richer set of shapes, and the chord on the seventh degree is still the odd one.
Pentatonics
A pentatonic tried on every degree — major where the chord's third is major, minor where it is minor. A note the attempt needs and the scale doesn't have is a hollow wedge; the attempt fails, nothing is extracted, and the small wheel keeps its hole. In a major scale six degrees pass and the seventh fails.
Minor
A minor scale is its relative major's seven notes from a different home, so the row is the same seven chords in a different order. Diminished and augmented chords are drawn like the rest, never hidden.
Harmonic and melodic minor
Raise the seventh, or the sixth and seventh, and the field changes: an augmented chord appears, its symmetry plain on its small wheel, and every pentatonic fails somewhere. The chips switch between the three minors.
Where you'll meet it
Pinned under Why the major modes, where it shares a frame with the circle of fifths, and on the Why Major Modes? page in the curriculum.