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Melody and harmony instruments
Lead and chordal instruments carry the tune and the harmonic colour — choose one clear lead voice and let the rest support it.
One lead, one bed
Melodic instruments split into two jobs. The lead carries a single identifiable line — solo cello, muted trumpet, saw-wave synth, slide guitar. The bed supplies the harmony underneath — piano, Rhodes, pads, strummed guitar, organ.
Most cluttered arrangements have two instruments both trying to be the lead. Assign the job explicitly in the prompt and the problem disappears: 'solo cello carries the melody, piano comps underneath' is unambiguous in a way that 'cello and piano' is not.
The bed is also where harmonic colour lives, so it is worth specifying its character separately from its identity. A piano playing simple triads and a piano playing extended ninth chords are two different arrangements sharing one instrument name.
Leads by character
- muted trumpet — intimate, nocturnal, jazz-leaning.
- solo cello — mournful, human, wide dynamic range.
- slide guitar — vocal-like, blues and Americana.
- saw-wave synth lead — bright, synthetic, cuts through anything.
- flute — light, pastoral, sits above a dense bed.
- electric guitar, overdriven — the default rock lead; specify clean or overdriven or it will choose.
- vibraphone — shimmering, soft attack, good for sparse arrangements.
Harmonic colour in one phrase
| Phrase | Effect | Fits |
|---|---|---|
| simple diatonic chords | plain, singable | folk, punk, country |
| extended jazz chords | rich, ambiguous | neo-soul, jazz, bossa |
| minor key, modal | dark, static | trap, darkwave, doom |
| suspended, unresolved | floating, unsettled | ambient, post-rock |
| gospel cadences | uplifting, resolving | soul, gospel, pop |
| chromatic movement | tense, cinematic | score, prog |
Example
Practice
Write a prompt with two melodic instruments and no role assignment, generate it, then rewrite it naming which instrument leads and which comps. Compare. Then keep everything fixed and change only the harmonic-colour phrase between diatonic, extended and modal — three generations that will show you how much of a song's emotional reading lives in the chords rather than the timbres.