This skill has two halves; when using it, be clear about which half you are in:
| Half | What it does | In which § |
|---|---|---|
| Function | Give the melody chords that make sense | §2–§5 |
| Colour | Make the chords that make sense sound good | §6–§7 |
★ The order cannot be reversed. First the functional skeleton, then the colour. Starting directly from colour results in "every chord is very sophisticated, but when connected you have no idea what it is doing".
Which sections to read depending on the task
| Symptom／Task | Read |
|---|---|
| You have a melody and need to add chords | §2 → §3 → §4 measure-by-measure workflow |
| The harmony is bland | §7 nine-step upgrade table |
| The harmony is too full, too fragmented | The ★ stop rules in §7 |
| You want a specific colour | §6 symptom→technique quick reference |
| One chord hangs for too long without changing | §6's クリシェ／sus4／suspension tones |
| You want the bass to move chromatically | §6's slash chords／裏 chords／passing diminished chords |
| How to harmonize in minor | §5 |
| Look up a ready-made progression | mc-progressions |
Boundaries: what this skill does not cover
| Not covered here | Where it belongs |
|---|---|
| Looking up a ready-made chord progression library (120 entries) | mc-progressions |
| Modulation | mc-modulation(This skill's §6 only givesharmonic introductions to modulation） |
| How to write the melody itself | mc-melody |
| How voices become independent, parallel fifths and octaves | mc-counterpoint |
| What instruments play the chords, voicing | mc-orchestration |
| Harmonic rhythm (how many chords per measure)'sgroovemeaning | mc-rhythm-groove §"How fast the harmony changes is also groove" |
| Harmonic vocabulary specific to a certain style | mc-style-*（L3） |
| A complete catalogue of scales／chords／tension tones | reference.md |
1. Must fill in before starting
| Required | Question |
|---|---|
| ① Key | Major or minor, which key.All degree symbols are based on it |
| ② Harmonic rhythm | How many chords per measure?★ One per measure for the whole piece is the most typical pattern |
| ③ What colour this section needs | Answer with §6's words, not "a bit nicer" |
| ④ Where it must be most stable, where it must be most unstable | Determines where the cadence goes |
2. The three functions
| Function | Character | Members |
|---|---|---|
| T（Tonic） | Stable | I、VIm(VIm is I's "stand-in") |
| S（Subdominant） | Mildly unstable, pushes toward D | IIm、IV |
| D（Dominant） | Unstable, wants to return to T | V、VIIm(♭5)(V is overwhelmingly common) |
D's instability must "resolve" to T; this psychological need is precisely the source of music's forward drive.
★ IIIm is excluded from this table——It is a chameleon: it can serve as both T and D, see §6.
3. Three types of cadences
| # | Type | Feel | Example |
|---|---|---|---|
| 1 | T → D → T | Like "stand up, bow, sit down"—simple and forceful | C→G→C（I→V→I）、Am→G→C（VIm→V→I） |
| 2 | T → S → D → T | Tension rises step by step, then resolves all at once to T—the most satisfying | C→F→G→C、Am→Dm→G→C |
| 3 | T → S → T | Returns to T without going through D; S→T is usually IV→I, i.e.the Amen cadence (plagal cadence) | C→F→C |
Chaining chords of the same function: chords of the same function can be strung together. Example C→Am→F→Dm→G→C (I→VIm→IV→IIm→V→I)— I+VIm strung together form T, IV+IIm strung together form S, and the whole is still T→S→D→T.
3.1 ★ Cadences and emotion: the only one that deals with lyrics (Kachulis)
None of the three harmony sources in this library deal with what the lyrics are saying; this layer comes from Kachulis, The Songwriter's Workshop: Harmony (p0163–0174):
| Cadence | Emotion |
|---|---|
| Perfect cadence V → I | Resolute |
| Half cadence (stopping on V) | Uncertain, creates tension |
| Deceptive cadence | An ambiguous surprise, and the three landing points each differ:V → VImin sorrowful; V → IV surprising; V → VI major triad a bright, cheerful surprise（p0169） |
| Plagal cadence IV → I | Religious feeling, spirituality |
| Mixed cadence (major borrowing minor ♭VI – ♭VII – I) | A mix of sorrow and joy, especially effective in rock blues |
The perfect cadence looks different in each mode (p0163–0165): major V–I; minor ♭VII–Imin or V–Imin; blues V7–IV7–I7; Mixolydian ♭VII–I; ★ Dorian has no perfect cadence。
3.2 Home and away from home: three section shapes (p0176–0193)
| Section | Shape |
|---|---|
| Verse plus chorus | Home – away – home |
| Verse | Home – away, stopping on V to push into the chorus |
| Bridge | Away – away, starting on a non-I and ending on V, with maximum tension |
Two ways to build a chorus: repeat using only one cadence; or use a cadence only on the thematic phrase, ★ avoid the tonic chord before the thematic phrase appears(p0182–0187). Section transitions: the verse stops on V and the chorus starts on I is a perfect-cadence transition; the chorus starting on VImin is a deceptive-cadence transition, giving a sense of surprise (p0191–0193).
★ Four harmonic criteria for section contrast(p0195): each section starts on a different chord; each section has at least one new chord;the perfect cadence appears only in the chorus; each section has a different phrase length. After writing, check against these four; two sections that fail all four will sound like the same section.
3.3 Chord color changes word meaning: coloring words and coloring phrases (Kachulis p0149–0160)
The same word on the same note, set to different chords, changes meaning:A major triad is full of hope, a power chord is forceful and confident, a minor triad is sad and introspective, a seventh chord is melancholy and sexy(p0149–0150). This library previously had no line from "chord → lyric meaning."
The process of coloring a phrase(p0152–0160): Find two or three important notes in the phrase,make a multi-column table of candidate chords, with each column corresponding to one measure, then try combining them; putting two chords in the same measure can create a bit of momentum. Pair it with a usage grouping (p0082): the group IImin–IIImin–IV–V, IV–V, IImin–V, VImin–V is a "tendency toward V" progression, specifically used to create tension and lead into the chorus.
4. The process of harmonizing measure by measure
- Confirm the basics: Write out the I, IIm, IV, V, VIm of this key and their functions, then write out the three types of cadences
- List candidates measure by measure: Take the melody notes of this measure and findwhose constituent notes include themthe diatonic chords
- The melody notes exactly equal the constituent notes of a chord → direct candidate (e.g., A·F·C → F)
- Multiple chords all contain them → tied candidates (e.g., B♭·D → B♭ or Gm, both are S)
- Decide with cadences: If the first three measures already form T→S→D, the fourth measure should return to T—choose a candidate with T function
- Ending rule: The whole piece landing on the most stable I is best
- T is both the endpoint and the starting point: In a functional chain like T S D T S T D T,a T is often shared by the two cadences before and after it
4.1 A complete example (F major, 3/4, 8 measures)
Candidate table: F(I,T), Gm(IIm,S), B♭(IV,S), C(V,D), Dm(VIm,T)
| Measure | Melody notes | Candidates | Decision |
|---|---|---|---|
| 1 | A·F·C | F (constituent notes match exactly) | F（T） |
| 2 | B♭·D | B♭ or Gm (both are S) | Either works |
| 3 | E·G·C | C | C（D） |
| 4 | A | F or Dm (both are T) | The first three measures are already T→S→D, so return to T here |
| 5–8 | Same method | B♭ → F → C → F | S→T→D→T, landing on I |
Result: F → B♭(or Gm) → C → F(or Dm) / B♭ → F → C → F
Rule of thumb: First try to fit things into the cadence framework as much as possible; it is a shortcut to progress.
★ Conditions for failure: Examples that violate theory are everywhere in real songs. Insisting that "cadences must absolutely hold" will itself produce unnatural progressions—stay flexible; there are exceptions to everything.
4.2 Two substitution rules for beginners (and their boundaries)
IIm and IV are interchangeable (within the S function group)—This one is the most stable. Ren Damin's "Popular and Jazz Harmony" groups ii, IV, and vi into the same subdominant function group, and "the most common is the mutual substitution of chords in the subdominant function group" (p0134): replacing I-IV-V7-I with I-ii7-V7-I or I-vi-V7-I makes the voice leading smoother (p0135). In jazz this goes further—after IV is replaced by ii7, in practice ii7 is actually more common than the original IV (p0280).
Replacing I with IIIm: the two sets of criteria are different, do not mix them up
- Taking the "chameleon" path (see §2, §6), when IIIm substitutes for I, its color is darker than VIm, and it is also more easily heard as a transition toward D.
- In Ren Damin's classical/jazz functional division, iii is instead classified asdominantFunctional group, in the same group as V and vii°7 (p0134); he states plainly that iii has weaker resolution power to I than V does, "the harmonic force of iii–I is relatively weak," and does not recommend letting iii stand in for I in a cadence (p0135). The more standard substitute he gives for I in major is actually VIm: because most of I's chord tones are contained in the VI chord, but thisholds only in major, and after the substitution the V following I usually also has to be rewritten as ii–V (p0279).
- Using secondary chords in succession itself has a cost: if in a passage almost all the primary chords are replaced by secondary chords like iii, vi, and ii, and it lands on VIm, the whole sound slides toward the relative minor and is no longer the original major (p0118, p0120 example 1-20).
5. Minor (based on harmonic minor)
The functional table for minor is isomorphic to the three cadences, but V must use a major triad/dominant seventh(from the raised seventh degree of harmonic minor), otherwise the resolving force of D→T disappears. For the detailed natural/harmonic/melodic minor comparison table, see reference.md。
6. Color techniques: symptom → technique quick reference
| Want | Preferred technique |
|---|---|
| More forward drive / more vivid | Secondary dominants, ii–V |
| More jazz / more stylish | Tension tones, chain ii–V, backdoor chords |
| 切なさ (wistfulness), a touch of shadow | Subdominant minor (S.M)、IIIm7 |
| Chromatic descending bass line | Slash chords, backdoor chords, passing diminished chords, クリシェ |
| The same chord is held too long, and you want internal motion | Cliché, sus4, pedal point |
| Avoid the clichéd feel of a plain dominant seventh | Minor dominant, backdoor chords, unresolved V7sus4 |
| Melancholy / cool / improvisational feel | Blues and blue notes |
| A complete change of atmosphere for a whole section | Modulatory intro (→ mc-modulation） |
| Reharmonize the whole section | §7 nine-step table |
6.1 Each technique in one sentence
| Technique | What it does |
|---|---|
| Slash chord | Specify the bass to create a smooth or chromatic bass line |
| IIIm7 | ★ Chameleon: it can serve as T (a substitute for I) and also as D (a substitute for V). The switch depends on context |
| Secondary dominant (Sec.D) | Place its V7 before any "chord temporarily acting as T" |
| ii–V | Split a dominant chord into IIm7→V7, doubling the forward drive |
| Backdoor chord (tritone substitution) | V7 → ♭II7. The bass moves chromatically, with a sharper flavor. Add ♭5 when it does not fit |
| Subdominant minor (S.M) | IV→IVm(6), or substitute ♭VI△7／♭VII7.The main source of wistfulness |
| Modal flavor (Dorian IV / minor dominant) | Borrow modal color to avoid the plainness of functional harmony |
| sus4 | Delayed resolution.Unresolved V7sus4 can completely avoid the cliché of the dominant seventh |
| Tension tones (9/11/13) | Add color without changing function |
| クリシェ (chromatic line) | The chord stays put while an inner voice moves chromatically—cures "the same chord is held too long" |
| Passing diminished chord | Fill into the whole-step gap |
| Pedal | Bass stays put, chords change above |
| Blues notes | The friction of ♭3, ♭5, ♭7 |
(For the complete usage of each, the available tension-tone table, and forbidden combinations, see reference.md。）
7. ★ Nine-step reharmonization table
Take a bland progression and try these in order. At every step, the ear is the final judge.
| # | What to do |
|---|---|
| 1 | Seventh-chord-ize(triads → seventh chords).Don't add them everywhere, watch the overall balance |
| 2 | Substitution：I ⇄ IIIm7/VIm7，IV ⇄ IIm7，V7 ⇄ VIIm7(♭5)/IIIm7 |
| 3 | Insert secondary dominants: before every "chord temporarily acting as T," try placing its V7 |
| 4 | Turn dominants into II-V: for every dominant seventh, check whether it can be split into IIm7→V7 |
| 5 | Tritone substitution on dominants: when you want a chromatic bass or a more aggressive flavor, V7 → ♭II7 |
| 6 | Borrow from the minor subdominant: IV→IVm(6), or ♭VI△7/♭VII7, for wistfulness |
| 7 | Insert dim7 into the whole-step gap、Slash chords for a smooth bass line、sus4 for delayed resolution |
| 8 | Sprinkle tension tones: add 9/11/13 according to the reference table |
| 9 | ★ Finally ask yourself: have I overdone it? |
7.1 ★ Step 9 is the most important step in this table
"Never chop the chords up too finely." Straightforward rock/pop especially needs to beware of wordiness—there are just as many cases where simple is best.
Self-check action: play the upgraded version and the original alternately. If you can't say what's better about the upgraded version, go back. Harmonic complexity is not a score; it is ameans。
7.2 Step-by-step upgrade demonstration
The same skeleton C → Am → Dm → G(I → VIm → IIm → V, looping progression):
| Step | Progression | Which step was used |
|---|---|---|
| Original | C → Am → Dm → G |
Diatonic triads |
| Seventh-chord-ized | C△7 → Am7 → Dm7 → G7 |
1 |
| Secondary dominants inserted | C E7 Am C7 F D7 G（I III7 VIm I7 IV II7 V） |
3 |
| Turned into II-V | C → Bm7(♭5) → E7 → Am → Em7(♭5) → A7 → Dm7 → G7 |
4 |
| Tritone sub + tensions | Em7 → E♭7 → Dm7 → D♭7 → C△7(9)(ending with a chromatic descending bass) |
5+8 |
| Add wistfulness | C → Am → Fm6 → G7sus4 → G7 |
6+7 |
★ Note that these six rowsare not better the further down you go. They are six different things. Which row to choose is determined by required item ③ in §1, not by "level of advancement."
8. Three commonly used skeletons (detailed table in mc-progressions）
| Name | Progression | Function |
|---|---|---|
| Loop progression | I → VIm → IIm → V | T→T→S→D。Can repeat infinitely, the skeleton of skeletons |
| Reverse loop | IIm → V → I → VIm | S→D→T→T. That is, a loop progression starting from the S section; in major keys it is used even more than the loop progression |
| Canon type | I → V → VIm → IIIm → IV → I → IIm → V | ★ Its charm lies inbeing able to extract a stepwise descending melodic line from the constituent notes of each chord, then turning upward at the last chord— The emotional effect of "a glimmer of hope suddenly appearing" |
The most common development of the reverse cycle: repeat twice, with the second landing on I; or when repeating, change the final VIm to VI major：
Dm→G→Em→Am ／ Dm→G→C→A
9. Correspondence with ARR-SPEC fields
| Field | Which section of this skill |
|---|---|
form[].harmony(degree) |
§2–§5 |
form[].harmony_letters(letter) |
Double notation of the same progression, a hard convention of this library |
| lint #9 (at least one section has a non-diatonic chord or modulation marker) | §6、§7 |
★ Double notation is a hard convention: degrees are used for thinking and transposition, letters are used for handoff and compiling into prompts. Writing only one is considered unfilled.
10. Must pass after writing
- Have the functional skeleton first, then add color, not the other way around
- For each section, the harmony must be able to state itsfunctional chain（T S D T…）
- The whole piece lands on I (only do the opposite if you want lingering resonance, and state the reason)
- The harmonic rhythm is not one bar per chord for the whole piece
- At least one section hasnon-diatonic chords（lint #9）
- After running through the nine-step tableask "is this too much?", and be able to say what is better about the upgraded version
- Degrees and lettersdouble notationcomplete
- Color techniques are chosen according to the needs of §1④, not according to "level of sophistication"
Appendix: Sources
- "初歩から身につく！コードの選び方マニュアル" + "もっと！思いどおりに作曲ができる本"— §2–§8 all main content. "Choosing chords" and "beautifying chords" are put in one skill because they are two stages of the same process, and splitting them into two skills would make the agent get stuck in between.
- Sposobin, "Textbook of Harmony"— The strict version of classical functional harmony, kept side by side with the Japanese-style onekept side by side: Sposobin governs the right and wrong of voice leading, the Japanese-style one governs how good or bad it sounds.The two do not conflict but have different criteria, see reference for the comparison table.
- Ren Damin, "Pop and Jazz Harmony"、 Levine, "The Jazz Theory Book"— A more complete version of tension tones and substitutions.
- Kachulis《The Songwriter's Workshop: Harmony》
- 120 ready-made progressions →
mc-progressions。