Modal interchange and borrowed chords

Borrowing without leaving

C major and C minor share a tonic and disagree about three notes: the third, the sixth and the seventh degrees. Modal interchange is the practice of taking a chord built on the minor set of notes and using it inside a piece that is otherwise in major. The key does not change. The tonic does not move. What changes is which version of the scale the harmony is drawing from at that moment.

This is what makes it different from modulation. A modulation moves the center. Modal interchange keeps the center and swaps the material around it, which is why a borrowed chord sounds like a shadow crossing the same room rather than like walking into a different one.

The ones you will actually use

• Minor iv — Fm7 in C. The most recognisable borrowed sound in the repertoire. Its Ab pulls down into the G and then into the third of the tonic, and it works after almost anything.
• bVI — Abmaj7 in C. A major seventh chord on the flat sixth. Wide and settled; often paired with bVII7 on the way back to the tonic.
• bVII7 — Bb7 in C. The backdoor dominant. Reaches the tonic from a whole tone below instead of from the fifth above.
• iiø7 — Dm7b5 in C. The minor key’s predominant used in a major one. It darkens the approach to the dominant without changing where the phrase is going.
• bIII — Ebmaj7 in C. The relative major of the parallel minor. It shares two notes with the tonic and steps sideways rather than forward.
• bII — Dbmaj7 in C. The Neapolitan: a major chord a semitone above the tonic, usually on its way to the dominant.

Telling borrowing from modulating

The test is whether the borrowed chord participates in a cadence to a new tonic. Fm7 arriving between two Cmaj7 chords is borrowing: C is still home before and after. Fm7 Bb7 Ebmaj7 is a ii-V-I in Eb, and if the music stays there it has modulated. Same first chord, different job, and only the context can tell you which.

The analyzer applies exactly this test. It marks a chord as modal interchange when it fits the parallel mode and does not take part in a cadence elsewhere, and it opens a separate key area only when a foreign key is confirmed by a cadence and holds for at least three chords.

Hear it in your own progression

Paste a progression of your own, or load one of these, and see where the device shows up.