One borrowed chord from a parallel mode in an otherwise diatonic loop is a cheap, strong hook

Modal interchange means borrowing a chord from a parallel mode (same root, different scale) for color — the source gives a major IV in a minor key (Dorian brightness) and a bVI or bVII in major (rock/cinematic weight). The key insight is the cost/impact ratio: ‘One borrowed chord in an otherwise diatonic loop is a cheap, strong hook.’ The loop stays mostly in-key, so the ear is oriented, but the single borrowed chord lands as an expressive departure. It is a practical composition shortcut — one chord swap turns a predictable progression into something with emotional depth.

Examples

A minor loop borrowing a major IV: chord('<Am7 Fmaj7 Dmaj7 G>') — the Dmaj7 (major IV, borrowed) supplies Dorian brightness. Or bVI in C major: chord('<C Ab G C>').

Assessment

Explain what makes modal interchange a cheap, strong hook. Give one concrete borrowed chord in a minor-key loop and name the mode it comes from.