Non-Diatonic Chords
Strict diatonic note and chord selection provides a gigantic amount of possibility for song-writing and solo'ing; however, it still places us inside a box that we occasionally want to escape. Non-diatonic chords allow us to do so. For any key, the possibilities for non-diatonic chords are huge. We limit ourselves to a few popular examples listed below. These fall under one of a few categories.
- Tonicizations use diatonic chords from other keys to temporarily alter the tonic center of the harmony.
- Borrowed chords use diatonic chords from other keys with the same tonic note.
- Chromatic chords cover all remaining cases. They maintain the tonic note but are non-diatonic to all the standard parallel keys/modes. They borrow from the chromatic scale, which allows any possible chord to be formed.
Contents
PreReqs
Tonicizations
Secondary Dominant
also called borrowed dominant
The most common borrowed chord is the V (or V7) of V chord, commonly notated as V/V or V7/V.
Other Secondary Harmonies
Notation
The "/" indicates that the chord is borrowed. The bottom or right side of the slash is the key that is being borrowed from. The left or top side of the slash indicates which chord from that scale is being used. V/V means the fifth diatonic major chord of the major key whose root is the fifth diatonic note of the current key.
Function
It is essentially a dominant function chord whose function is to resolve to the dominant chord of the current key. That chord then resolves to the I or i chord. V/V - V - I.
Example
In C Major, the progression would be D - G - C. D is borrowed, as Dm is the diatonic chord. The raised F# that makes it a major chord also gives it the dominant function to resolve a half step to G, as part of the G chord.
If the D Major chord did not resolve to G Major, demonstrating its dominant functionality, we might alternatively analyze this as a II or borrowed major from some other key.
In the key of G Major, V/V would be an A Major chord. Let's look at both keys:
| V/V | V | I | |
|---|---|---|---|
| C Major | D | G | C |
| G Major | A | D | G |
Notice that both progressions feature D - G. In G Major, it's V - I. In C Major, it's V/V - V. G Major is built on the fifth note of C Major; it is the V key. In both progressions they contain the same basic dominant-resolution feel, yet by occurring at different parts of the V/V - V - I progression, they serve somewhat different functions.
Borrowed Chords
Chords can also be borrowed from the parallel major/minor of the current key.
Borrowing from Minor
When using a major key, chords can be borrowed from either the parallel natural or harmonic minor keys:
| iio | bIII | iv | bVI | bVII | viio7 | |
|---|---|---|---|---|---|---|
| C Major | D dim | Eb | Fm | Ab | Bb | Bo7 |
| G Major | A dim | Bb | Dm | Eb | Fb | Fo7 |
| Borrowed From |
Nat/ Hrm |
Nat | Nat/ Hrm |
Nat/ Hrm |
Nat | Hrm |