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.