Jp Chord Selection

Harmonizing a Melody with Chords (メロディへのコードづけ)

Methodology source: Sho Ueda, Shoho kara Mi ni Tsuku! Chord no Erabikata Manual ("Learn from the Basics! A Manual for Choosing Chords", Rittor Music), Introduction through Chapter 2. Core idea: harmonizing a melody is like a jigsaw puzzle (パズル) — a melody never has only one valid harmonization, but "knowledge" is the driving force that gets you closer to the right answer.

Workflow Overview

Given a melody, work through the following steps in order:

1. Identify the key — the biggest shortcut to harmonization
2. List the diatonic chords (ダイアトニックコード) — this immediately narrows the candidate pool
3. Arrange them by cadence (ケーデンス) — match melody notes measure by measure, fitting them into the T→S→D→T framework
4. Handle non-chord tones (非和声音) — decide which melody notes are "decoration" and confirm each one resolves
5. Substitute / apply staple progressions — replace I with IIIm, IIm with IV, or drop in one of the three staple progressions directly
6. Upgrade to 7ths — function unchanged, sound more stylish (オシャレ)

Simplifying assumption (beginner default): one chord per measure; once fluent, two per measure is fine.

Step 1: Identify the Key

1-1 Reasoning from Accidentals

Memorize the two orders in which accidentals are added (key-signature rules):

• Order of ♯s: ファ→ド→ソ→レ→ラ→ミ→シ (F → C → G → D → A → E → B)
• Order of ♭s: シ→ミ→ラ→レ→ソ→ド→ファ (B → E → A → D → G → C → F — exactly the ♯ order reversed)

Reasoning procedure:

1. Tally the ♯/♭ notes in the melody and compare against the orders above. Example: only F♯ and C♯ appear, G carries no ♯ → most likely a key with 2 sharps.
2. Each key signature maps to a pair of relative keys (平行調, relative major/minor) as candidates. 2♯ → D Major or B Minor.
3. The key to telling major from minor: the minor scale's 7th degree — the leading tone (導音) — is frequently raised a semitone by accidental (a consequence of the harmonic minor scale).
   • B Minor's leading tone is A♯: if A is never raised in the melody → conclude D Major.
   • If the melody frequently shows "an accidental sharp outside the key signature that happens to be some minor key's leading tone" → interpret it as that minor key.

1-2 Distinguishing "Scale Tones" from "Ornamental Notes"

Accidentals (変化記号) in a melody come in two identities:

• 音階固有音 (notes inherent to the key's scale): the sharps/flats the scale itself carries
• 装飾音 (ornamental notes): temporary decoration, unrelated to the key

Note-by-note elimination rules:

Worked note-by-note example (♯s appear on ラ, ド, ファ; ♭ appears only on ミ):

1. ド: both C♯ and C♮ occur → C♯ is very likely just decoration → the true note is C♮;
2. ラ♯: if it were a scale tone, then by the ♯ order G and D would also have to be sharped, and they are not → ornamental; the true note is A♮;
3. ミ♭: an E♮ sits adjacent, and it appears to set up a descent to D → ornamental;
4. ファ♯: cannot be eliminated directly → assume it is a scale tone: "a key where C is ♮ and F carries a ♯" = G Major or E Minor;
5. Leading-tone test: E Minor's leading tone is D♯, which should appear frequently; the score has none → conclude G Major.

1-3 Key Identification Is Inherently Ambiguous

The same melody may admit two legitimate readings (e.g., C Major with C→G→C, or A Minor with Am→E7→Am). In that case, decide from context and the mood (ムード) of the whole piece. Beyond theoretical deduction, the intuition of "feeling" the key from the melody matters most — play it and sing it before reasoning.

Key Signature Quick Reference

Step 2: List the Diatonic Chords (ダイアトニックコード)

Chain of logic: key determined → diatonic chords can be listed → candidate chords are fixed. Diatonic chords = chords built by stacking thirds on each scale degree, using only notes within that key's scale.

Major-Key Diatonic Chords (C Major as example)

Transpose by degree to any major key, e.g. F Major: F(I)–Gm(IIm)–Am(IIIm)–B♭(IV)–C(V)–Dm(VIm)–Em(♭5)(VIIm(♭5)).

In practice, master these 5 first: I, IIm, IV, V, VIm.

• IIIm is a "chameleon chord that changes its role by context" — skip it at the beginner stage;
• VIIm(♭5) is rarely used as D; for the dominant function, prefer V.

Chord Construction Rules (in Semitones)

Interval quick reference (semitones between two notes):

The four triads (トライアドコード, triad chords; semitones stacked upward from the Root):

Principal 7th chords (triad + 7th; parentheses give semitones from Root to the 7th):

Fast method for building any chord (E♭ as example): first fix the outer frame — a perfect 5th above the Root (E♭→B♭, 7 semitones, never wrong) — then fill the inside: 4-below/3-above for Major, 3-below/4-above for Minor.

Supplementary general rules:

• If the constituent notes match, the symbol stays the same regardless of how open the voicing is or whether notes are doubled.
• 転回形 (inversion): when the Root is not the lowest note, write C(onG) or C/G (read "C on G"); inversion does not change the Root.
• A chord symbol is only a rough representative of "the harmony governing this passage" — notes outside the symbol sounding on the page is perfectly normal (those are non-chord tones; see Step 4).

Degree Name (ディグリーネーム) Notation Rules

This skill uses dual notation throughout — "letter + degree" — with degree rules as follows:

1. The Roman numeral indicates "which scale degree of the current key the chord's Root sits on"; the quality suffix carries over as-is: Dm→IIm, G7→V7, C△7→I△7;
2. Non-diatonic chords are labeled by the Root's alteration relative to the scale tone: C♯dim7 in C Major → ♯Idim7;
3. Change the key and the degree changes: the chord C is I in C Major but IV in G Major;
4. Minor-key degrees are referenced to the relative major: A♭ in C Minor → ♭VI.

Step 3: Arrange by Cadence (ケーデンス)

The "grammar" of chord ordering is called ケーデンス (cadence; the German-derived term is カデンツ).

The Three Functions

D's instability must "resolve" onto T; this psychological need is precisely the source of musical forward momentum. IIIm is excluded from this list (chameleon).

The Three Cadence Types

1. T → D → T: like "stand up, bow, sit down" — simple and forceful. Examples: C→G→C (I→V→I), Am→G→C (VIm→V→I)
2. T → S → D → T: tension rises gradually, then resolves onto T in one stroke — the most "satisfying". Examples: C→F→G→C (I→IV→V→I), Am→Dm→G→C (VIm→IIm→V→I)
3. T → S → T: returns to T without passing through D; S→T is usually IV→I, commonly called the アーメン終止 (Amen cadence / plagal cadence). Example: C→F→C (I→IV→I)

同機能の連用 (consecutive use of same-function chords): chords of the same function may be chained. Example: C→Am→F→Dm→G→C (I→VIm→IV→IIm→V→I) — I+VIm chained as T, IV+IIm chained as S; the whole is still T→S→D→T.

Measure-by-Measure Harmonization Procedure

1. Confirm the essentials: write out the key's I, IIm, IV, V, VIm with their functions, plus the three cadence types.
2. List candidates per measure: take that measure's melody notes and find the diatonic chords whose constituent notes contain them.
   • Melody notes exactly match a chord's tones → direct candidate (e.g., measure notes A·F·C → F);
   • Multiple chords contain the notes → parallel candidates (e.g., B♭·D → B♭ or Gm, both S).
3. Adjudicate by cadence: if the first three measures already form T→S→D, measure four should return to T — pick the T-function candidate (F or Dm both work; choose by taste).
4. Ending rule: closing the piece on the most stable chord, I, is best.
5. T is both endpoint and starting point: in a function chain like T S D T S T D T, one T is often shared by the cadence before and the cadence after it.

Worked Example: F Major, 3/4 Time, 8 Measures

First write out the candidate table: F(I,T), Gm(IIm,S), B♭(IV,S), C(V,D), Dm(VIm,T). Then measure by measure:

Result: F → B♭(or Gm) → C → F(or Dm) ／ B♭ → F → C → F; overall function chain T S D T S T D T.

Second major-key example (C Major, 8 measures, melody containing non-chord tones): C → F → Dm → G ／ C → Am → Dm → G → C Degrees I → IV → IIm → V ／ I → VIm → IIm → V → I; functions T → S (IV and IIm chained) → D ／ T (I and VIm chained) → S → D → T — the cadence completes twice. Rule of thumb: trying to fit the cadence framework as much as possible first is the shortcut to improvement.

Caveat: real songs are full of examples that do not obey the theory. Insisting "the cadence must hold absolutely" can itself produce unnatural progressions — stay flexible and remember that "everything has exceptions."

Step 4: Handling Non-Chord Tones (非和声音)

Concepts

• 和声音 (Chord Tone): a melody note that belongs to the current chord's constituent notes.
• 非和声音 (Non-Chord Tone): a melody note that does not belong to the current chord's constituent notes (e.g., a D over a C chord).

All chord tones → correct but overly plain; saturated with non-chord tones → jarring (チグハグ). Balancing the ratio is a matter of experience and taste. Non-chord tones are "accessories," not "obstacles" — their urge to return to a chord tone generates forward momentum, a "slightly naughty charm (ちょいワルな色気)."

Three Behavioral Traits

1. They "resolve" (非和声音の解決): a non-chord tone is essentially an altered form of a chord tone; most resolve to the nearest chord tone, and they may also resolve toward a constituent note of the next chord.
2. They cannot be left hanging: a non-chord tone that jumps into the next chord unresolved sounds wrong. Fix: insert a better-fitting chord that turns the note into a chord tone (e.g., an awkward A between C→G — insert F, giving C→F→G).
3. They come in four types:

Practical Implications

• For the same melody, which note you interpret as the chord tone changes the harmonization (the same melody can take Dm→G or C→Dm) — adjudicate via cadence and surrounding context.
• Self-check after harmonizing: circle every non-chord tone and confirm each belongs to one of the four types and has a resolution destination.
• Reverse application: when writing accompaniment, deliberately embedding "non-chord tone → resolution" motion yields a forward drive that plain arpeggios cannot provide.

Minor-Key Harmonization (Based on the Harmonic Minor Scale)

The rules are (almost) identical to major — arrange diatonic chords by cadence. "Almost," because minor has three scales, and the diatonic chords differ subtly depending on which scale you use.

The Three Minor Scales

1. 自然的短音階 (natural minor scale): whole–half–whole–whole–half–whole–whole; the minor key's signature is determined by this scale.
2. 和声的短音階 (harmonic minor scale): raises the 7th degree a semitone, creating the 導音 (leading tone) — entering the tonic from a semitone below; the leading tone is written with an accidental. Most important for harmonization; must be memorized.
3. 旋律的短音階 (melodic minor scale): ascending, the 6th degree is also raised (eliminating the augmented 2nd, easier to sing); the descending form = natural minor.

Diatonic Chords of the Harmonic Minor Scale (C Minor as example)

Diatonic chords of all three scales compared (C Minor, for reference):

• Minor-key degrees are labeled relative to the relative major (A♭ in C Minor is written ♭VI).
• ♭IIIaug has a peculiar sound and is almost never used in ordinary cadences; the natural minor's ♭III can be viewed as "the relative major's I."
• ♭VI is treated as T in classical theory, but jazz/pop often treats it as S (its notes are close to IVm); this method adopts the easier-to-grasp classical reading, T.

In practice, master these 5 first: Im, IIm(♭5), IVm, V, ♭VI (in C Minor: Cm, Dm(♭5), Fm, G, A♭; functions T, S, S, D, T).

Basic minor example: A Minor harmonized as T→S→D→T gives Am → Bm(♭5) → E → Am (Im → IIm(♭5) → V → Im).

Key Technique: Inserting the Relative Major's V→I

Inserting the relative major's (平行長調) V→I into a minor progression creates a momentary brightness like "light breaking through a gap in the clouds" — extremely common.

C Minor 8-measure demonstration: Cm → Fm → B♭ → E♭ → A♭ → Dm(♭5) → G → Cm Degrees: Im(T) → IVm(S) → [E♭ Major's V(D) → I(T)] → ♭VI(T) → IIm(♭5)(S) → V(D) → Im(T)

The key to returning to the home key is using a common chord as the "hinge" (蝶番, ちょうつがい): A♭ is IV from E♭ Major's viewpoint and ♭VI from C Minor's, sliding the music smoothly back into the minor key.

Minor-Key Worked Example (A Minor, 3/4 Time, 8 Measures)

Exactly the same procedure as major: first list Am(Im,T), Bm(♭5)(IIm(♭5),S), Dm(IVm,S), E(V,D), F(♭VI,T), then match melody notes measure by measure and adjudicate by cadence. Sample solution:

Am → Dm → G → C ／ F → Bm(♭5) → E → Am

• First half: Im(T) → IVm(S) → [C Major's V(D) → I(T)] — the relative major mixed in mid-course;
• Second half: ♭VI(T) → IIm(♭5)(S) → V(D) → Im(T); the common chord F (C Major's IV / A Minor's ♭VI) acts as the hinge (蝶番);
• This progression is identical to the classic Autumn Leaves (枯葉); harmonizing measure 5 with Dm (IVm, S) is also fine — Dm is likewise a common chord of both keys.

Step 5: The Three Staple Progressions and Substitution

Substitution Rules (Two, for Beginners)

• Within a progression, I (T) may be replaced by IIIm (IIIm is I's substitute);
• In the S segment, IIm may be replaced by IV (and vice versa; same function, interchangeable).

Staple #1: 循環コード (Cyclic Progression)

I → VIm → IIm → V (C Major: C → Am → Dm → G), functions T→T→S→D. "Cyclic" means it can repeat indefinitely — the staple of staples (Stand by Me, etc.). Chained variant example: C→Am→Dm→G ／ Em→Am→F→G (I→VIm→IIm→V ／ IIIm→VIm→IV→V).

Staple #2: 逆循環コード (Reverse Cyclic Progression)

IIm → V → I → VIm (C Major: Dm → G → C → Am), functions S→D→T→T — i.e., the cyclic progression started from its S segment. Used mainly in major keys, arguably even more often than the cyclic form (ヘビーローテーション (Heavy Rotation), 君の瞳に恋してる (Can't Take My Eyes Off You), etc.). Most common development: repeat twice, ending on I the second time; or on the repeat, turn the final VIm into a VI major triad: Dm→G→Em→Am ／ Dm→G→C→A (IIm→V→IIIm→VIm ／ IIm→V→I→VI).

Staple #3: パッヘルベルのカノン型 (Pachelbel's Canon Type)

I → V → VIm → IIIm → IV → I → IIm → V (C Major: C → G → Am → Em → F → C → Dm → G). Especially common in J-POP (ハナミズキ (Hanamizuki), チェリー (Cherry), etc.). Its charm: from the constituent notes of the chords you can extract a stepwise descending melodic line that turns upward at the final chord — an emotional effect of "a sliver of hope suddenly emerging," extremely useful for both songwriting and accompaniment.

Transposition: move it by degree to any key (e.g., F Major: F C Dm Am B♭ F Gm C).

Step 6: Upgrading to 7ths

Core Conclusion: 7th Chords Have Exactly the Same Function as Their Triads

Major-key diatonic 7th chords (ダイアトニック7thコード, C Major):

So direct substitution is fine: C→F→G→Am (I→IV→V→VIm) ⇒ C△7→F△7→G7→Am7, no problem at all. Five to remember is enough: I△7, IIm7, IV△7, V7, VIm7.

V7 Is the Protagonist That Pulls the Music Forward

The most frequently used diatonic 7th is V7 (属七の和音, the dominant 7th chord): structurally the union of the triads V and VIIm(♭5) (G + Bm(♭5) = G7). Its Dominant pull is exceptionally strong — use it actively.

7ths Widen Your Harmonization Options

A melody note may be interpreted as the chord's 7th to justify a 7th chord (e.g., melody note B over C → harmonize with C△7). Many "nothing seems to fit" melodies suddenly open up. Even when the melody contains no 7th, you may use a 7th purely for the stylish sound.

Minor-Key 7ths (Harmonic Minor Scale, C Minor)

The other two scales' 7th versions (for reference, C Minor):

• Natural minor: Cm7(Im7,T)・Dm7(♭5)・E♭△7(♭III△7,T)・Fm7・Gm7(Vm7,D)・A♭△7・B♭7(♭VII7,S)
• Melodic minor (ascending): Cm△7・Dm7(IIm7,S)・E♭△7(♯5)(×)・Fm7・G7・Am7(♭5)・Bdim7

Practical points for minor:

• Im△7 has a fairly jarring sound; the natural minor's Im7 is usually substituted for it;
• → Five to remember in minor: Im7, IIm7(♭5), IVm7, V7, ♭VI△7;
• The relative major's V→I can likewise be 7th-ized (V7→I△7, or 7th-ize only one of the two).

C Minor 8-measure comprehensive demonstration: Cm7 → Fm7 → B♭7 → E♭△7 → A♭△7 → Dm7(♭5) → G7 → Cm7 (Im7 → IVm7 → [relative major E♭'s V7→I△7] → ♭VI△7 → IIm7(♭5) → V7 → Im7)

Practical example of minor reverse-cycle + 7th-ized relative major (D Minor, 8 measures): Dm7 → Gm7 → C7 → F△7 ／ B♭△7 → Em7(♭5) → A7 → Dm The first half is [relative major F Major's V7→I△7] (C7→F△7); then the common chord B♭△7 serves as the hinge (蝶番) back to D minor (IIm7(♭5)→V7→Im).

Dosage Warning

7ths are rich and complex in sound — you need not use them everywhere: restricting yourself to V7 alone, or adding only IIm7, gives a calmer sound less likely to clash with the melody. Do not overdo it — "observe the dosage and directions; use correctly."

Classic-Song Proof: Less Is More

草競馬 (Camptown Races) (S. Foster, F Major) uses only 3 chords in the entire song: F(I), C7(V7), B♭(IV):

• Section [A]: F ↔ C7 — a plain alternation of T and D — the music just keeps pressing forward;
• Section [B]: the S-function B♭ makes its first appearance — a chord never heard before transforms the color, producing a flowing "the view suddenly opens up" sensation;
• Section [C] returns to C7→F to close.

Lesson: just 3 chords plus a simple melody can build a three-dimensional world; the "late arrival" of the S chord is a classic device for creating sectional color change. When harmonizing your own melody, you need not chase richness in every measure — first decide "which function makes its entrance in which section."

Quick FAQ

Q: The melody notes in a measure don't fully belong to any common chord? Treat the misfit notes as non-chord tones (confirm they belong to one of the four types and have a resolution destination) and choose the chord from the remaining notes; or interpret the note as a 7th and use a 7th chord; failing that, consider two chords in the measure, assigning the note to the second chord that fits it.

Q: Two candidate chords both make sense — which to pick? Function first — pick the chord whose function the cadence demands; among same-function parallel candidates (e.g., B♭ vs Gm, F vs Dm), choose by personal taste and color. There is no single correct answer.

Q: The melody sounds sad — can I conclude it's minor? No. Reason from accidentals plus the leading-tone test (Step 1); if genuinely ambiguous, decide by context and the piece's overall mood, and verify by actually playing and singing.

Q: Must each measure have exactly one chord? Beginner default is one per measure; when melody notes are dense or the function needs to switch, two chords per measure (usually split on the strong beat) is very common.

Q: Want a flash of brightness in a minor progression? Insert the relative major's V→I (or V7→I△7), then slide back to the home key via a common chord (the hinge, 蝶番).

Q: The result sounds too bland? Try in order: same-function substitution (IIIm for I, IV for IIm) → apply a staple progression → localized 7th-izing (V7 first) → have an S-function chord make a "late arrival" in a new section for a color change.

Quick Checklist

Self-check after harmonizing a melody:

• Key identification is grounded (accidental order + leading-tone test), and the relative key's alternative reading was considered
• All chords used are within the key's common 5 (major: I/IIm/IV/V/VIm; minor: Im/IIm(♭5)/IVm/V/♭VI), with justified exceptions
• The function chain reduces to the three cadence types (including same-function chaining), ending on I (or a deliberately open ending)
• Every melody note in each measure is either a chord tone or one of the four non-chord tone types with a resolution
• Minor keys harmonized from the harmonic minor scale; for momentary brightness, consider the relative major's V→I plus a common-chord "hinge" (蝶番) return
• 7ths used only where needed, V7 first

Terminology Quick Reference (Japanese → English)