Hearing the same melody harmonised with bright chords (I, IV, V) and then dark chords (ii, iii, vi) reveals what’s actually true about the seed’s emotional character. One version will feel right. That feeling is compositional instinct.
1Build the light harmonisation. Use only G (I), C (IV), and D (V) beneath your seed. These are the three major chords of G major — bright, resolved, open. They’ll always sound correct underneath a G major melody. Play this version three times.
2Build the dark harmonisation. Use only Am (ii), Bm (iii), and Em (vi). These are the three minor chords of G major — more ambiguous, more interior, less resolved. The melody note that sat comfortably over G major as the 5th now sits over Am as something else entirely. Play this version three times.
3Compare them directly. Light version: play once. Dark version: play once. Light again. Dark again. Listen specifically for the moment where the character feels most different. That moment is the melodic note where the harmonic context makes the biggest difference.
4Try one chord from each group. Verse idea: dark harmonisation (Am or Em beneath the seed). Chorus idea: light harmonisation (G or D beneath the same seed). This is literally verse-to-chorus contrast built from harmonisation alone — the melody unchanged, the emotional world completely different.
5Choose the version that feels truer to what the seed is trying to say. Not safer, not more familiar — truer. If the seed came from something dark or searching, the Am version probably fits. If it came from something open or hopeful, the G version probably fits. Trust the instinct. You can always use the other version for a different section.
TIPThe choice between bright and dark harmonisation is not a technical decision — it’s an emotional one. Every chord you place beneath a melody is an editorial choice: this note means this in this context. Making that choice deliberately, rather than defaulting to the most familiar chord, is the beginning of having a compositional voice. The chord you choose reveals what you think the melody is saying.