Kaplan Harmonic Movement System
A Chord Framework That Includes the Exceptions
Description
The Kaplan Harmonic Movement System is a method of composing or improvising chord progressions based entirely on legal movement types between triads.
It does not rely on key, function, memory, or destination. Each chord is evaluated solely by how it moves to the next.
Core Rule
A chord movement is legal if the combination of chord type, direction, and semitone distance occurs between two diatonic triads in any major key.
It doesn’t matter whether those chords exist in the current key.
The move is valid as long as it occurs somewhere in diatonic harmony.
Semitone Measurement
All motion is measured in semitones (chromatic distance).
There is no use of “steps” or “interval names.”
C → C♯ = up 1 semitone
C → D = up 2 semitones
C → A = down 3 semitones
Only the number of semitones matters — not what the interval is called.
Scope
This system is built exclusively from diatonic triads 1–6 in the major scale:
I, ii, iii, IV, V, vi
This version of the system does not utilize diminished chords and therefore is not built with movements to or from the vii° chord.
How It Works
At any given moment:
You are on a major or minor triad
You may move to another triad only if that move — by semitone distance, direction, and type — occurs between two diatonic chords in some major key
There are:
No keys to track
No functions to assign
Just one question: Am I allowed to make this move?
The idea is that if a particular move sounds “normal” based on diatonic harmony in some key,
then the same movement should sound reasonable at any time.
It may be unique in context, but it won’t sound dissonant or abnormal.
It’s Easier Than It Sounds
Each triad (major or minor) has a limited set of legal moves.
These are not invented — they reflect how chords move in real music.
✅ Legal Moves from a Major Chord (with examples)
🔼 Upward Moves
up 2 → major or minor e.g. (I → ii) or (IV → V)
up 4 → minor e.g. (I → iii)
up 5 → major e.g. (I → IV)
up 7 → major e.g. (I → V)
up 7 → minor e.g. (IV → ii)
up 9 → minor e.g. (I → vi)
up 10 → major e.g. (V → IV)
up 11 → minor e.g. (IV → iii)
🔽 Downward Moves
down 1 → minor e.g. (IV → iii)
down 2 → major e.g. (V → IV)
down 3 → minor e.g. (I → vi)
down 5 → major e.g. (IV → I)
down 5 → minor e.g. (V → ii)
down 7 → major e.g. (V → I)
down 8 → minor e.g. (I → iii)
down 10 → minor e.g. (I → ii)
down 10 → major e.g. (V → IV)
✅ Legal Moves from a Minor Chord (with examples)
🔼 Upward Moves
up 1 → major e.g. (iii → IV)
up 2 → minor e.g. (ii → iii)
up 3 → major e.g. (ii → IV)
up 5 → major or minor e.g. (ii → V) or (iii → vi)
up 7 → minor e.g. (ii → vi)
up 8 → major e.g. (iii → I)
up 10 → major or minor e.g. (ii → I) or (iii → ii)
🔽 Downward Moves
down 2 → major or minor e.g. (ii → I) or (iii → ii)
down 4 → major e.g. (iii → I)
down 5 → minor e.g. (vi → iii)
down 7 → major or minor e.g. (ii → V) or (iii → vi)
down 9 → major e.g. (ii → IV)
down 10 → minor e.g. (ii → iii)
down 11 → major e.g. (iii → IV)
🧭 Relative Chord Labels (Nashville System)
Another way to analyze the results is to assume that the starting chord is the root of a key (major or natural minor).
This allows each legal destination chord to be labeled using Nashville Number notation — including whether the chord is diatonic or non-diatonic in that context.
🎼 From a Major Chord
2 (non-diatonic)
2m (diatonic)
3m (diatonic)
4 (diatonic)
5 (diatonic)
5m (non-diatonic)
6m (diatonic)
♭7 (non-diatonic)
7m (non-diatonic)
🎼 From a Minor Chord
♭2 (non-diatonic)
2m (non-diatonic)
♭3 (diatonic)
4 (non-diatonic)
4m (diatonic)
5m (diatonic)
♭6 (diatonic)
♭7 (diatonic)
♭7m (non-diatonic)
🎵 Freedom Without Dissonance
This is non-functional harmony, but it never feels random.
Each move is grounded in some diatonic reality, even when the overall progression does not conform to one.
At any moment, everything sounds normal.
There’s no need to look back — and no need to plan ahead.
It’s a system that encourages present-mindedness.
The past doesn’t matter and the future is unknown.
Any chord is possible a few moves out.
The only thing that matters is what the present harmony is — and the next pleasant-sounding move.
All purely diatonic progressions fall within these 9-move boundaries.
In addition, a great many common exceptions to strict diatonic harmony also arise naturally from this system — without requiring explanations like “modal borrowing” or “chromatic substitution.”
No special justification is needed.
The movement is valid simply because it occurs in diatonic music somewhere.