Modal Interchange
Borrow a chord from the key with the same root and the opposite quality, drop it into your progression, and carry on as if nothing happened. It is how a bright major song gets one bar of shadow without changing key, and it is everywhere in pop.
- 1 borrowed chord
- the minor iv is the classic
- anywhere in the phrase
which styles use it
- Pop
- Film music
- Rock & folk
- Soul & R&B
In short
C major and C minor share a root and differ in three notes. Modal interchange takes a chord built from the other one and uses it in your key. The most common borrowing by far is the minor iv in a major key: in C that is F minor where F major belongs. The flattened seventh, the flattened sixth and the flattened third get borrowed constantly too.
The borrowed chord works because it is both familiar and wrong. Your ear knows the root, recognises the shape, and registers that one note has gone somewhere it should not.
Where it sits in the sentence
- The minor iv is the place to start
It works in almost any major key song and it is instantly recognisable once you know it.
- Keep it brief
One bar of borrowing is a colour. Four bars of it is a key change, and a different subject.
- Return cleanly
Go back to a strong diatonic chord afterward so the borrowing reads as a detour rather than a wrong turn.
Where you run into this
- In pop ballads, where the minor iv before the final chorus is close to a convention.
- In film music, where borrowing is how a cue turns without modulating.
- In rock, where the flattened seventh and flattened sixth are so common that people forget they are borrowed at all.
The borrowings side by side
One major key loop, played four times: plain, with the minor iv, with the flattened VII, and with the flattened VI. Same key throughout, and four different shades.