Chord borrowing and functionnality in the chord progression

[François T]

Hello everybody, I’m new to music theory (fascinating topic) and I have a beginner’s question :

If for example the (diatonic) chord progression in A minor is a i-VII-VI-v (Am7 – G7 – FM7 – Em7 if I’m not mistaking) what happens if for example a Gm7 is played after (or instead of) the GM7 ? Is the borrowed chord retains the VII function within the chord progression or does it acts like for example the I of a G minor scale ?

I’m sorry if it sounds a bit confusing but it’s not crystal-clear in my mind yet, the simplified version of my question is : Does the modification of a chord to include non-diatonic notes preserve the function within the chord progression or does it shifts it ?

Thank you for reading and have a great day !

[Jean-Michel G]

Bonjour François 😉

First, I would like to point out that a diatonic progression in Am is very unlikely to contain a G7 (G B D F), because that chord is the dominant 7th chord of the relative major key (i.e. C), and therefore strongly pulls toward that C chord.
It also cannot be a GM7 (G B D F#) since that chord is not diatonic to Am nor to C.

So your diatonic progression should be: Am – G – F – Em(7).

And now for your question…

In (contemporary) functional harmony, there are three types of chords:
1) Tonic chords (T)
Those are all the chords that do not contain the 4th degree of the tonality (the subdominant)
2) Subdominant chords (SD)
Those are all the chords that contain the 4th degree (the subdominant), but not the tritone
3) The dominant chords (D)
Those are all the chords that contain the tritone (consequently, they obviously contain the subdominant, since the tritone is the interval between the 4th degree and the leading tone)

As a general rule, all the chords within the same group are functionally equivalent and can therefore be substituted to one another. (Classical harmony is more restrictive).

So, let’s classify the chords of your progression and find out what their function is.
Since the V chord is Em7 (and not E7), we seem to be in the natural minor mode and so there will be no dominant chord since there is no leading tone.
Am: that’s clearly a tonic chord!
G: contains the 4th degree so it is an SD-chord
F: does not contain the 4t degree and therefore it is a T-chord
Em7: contains the 4th degree and is therefore an SD-chord. The reason it (mildly) wants to resolve to Am is due to the root V – I movement.

But if we change your progression to be: Am – G – F – E7 then that E7 chord becomes of course a D-chord with a much stronger pull towards Am. Sharpening the 7th degree for the benefit of the V chord turns it into a D-chord and means that we temporarily switch to the harmonic minor mode.

When you borrow a chord from a parallel key, the original function will or will not be retained depending on the chord tones.
For example, substituting a Gm7 to that G chord: Am – Gm7 – F – E7 does not change its SD function since Gm7 (G Bb D F) contains the 4th degree but not the tritone.

I hope this is clear and I hope it helps!
A bientôt!

[François T]

Bonjour et Merci Jean-Michel !

Sorry for the late reply and thank you for this clear explanation, it is clear that I have a loong way to go to be able to have a solid grasp on these concepts ! (I see that as a lifelong learning)

I am not sure to grasp decently the concept of the (T/SD/D) chords.
From what I think I understood if we are in C major for example (with quadrad chords):
– The Tonics chords would be C, E, A (as they have not the 4th degree, F in this instance)
– The Subdominants chords would be D and F
– The Dominant chord would be G and B (as they both have the tritone between the 4th degree F and the subdominant B)

Merci encore et bonne journée !

[Jean-Michel G]

Hi François,

Yes, your summary is correct.
There are actually three other diatonic chords:
– I6 (e.g. C6 in C major) is also a T-chord
– IV6 (e.g. F6 in C major) is also an SD- or PD-chord
– ii6 (e.g. Dm6 in C major) is also a D-chord

That being said, I have to make two observations – just in case a picky music theorist passes by 😉
– In classical harmony, the iii and vi chord don’t have a predefined function.
– Ultimately, the function of a chord depends on the context in which it operates; there are cases where the melodic movements of the soprano and bass voice of the chord voicings force sole chords to operate according to a function that they shouldn’t have based on the definitin I gave in the previous post.

But as a general rule, yes, you are correct.

The rationale for this classification is that, in classical harmony, a piece of music is considered to be a journey going from stable consonant tonic chords through slightly less stable and slightly less consonant pre-dominnat chords, to very unstable and dissonant dominant chords, and then back to stability and consonance.

A bientôt!
JM

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