What is the functional description of the I-III-VI(7) progression?

How do you functionally describe the I-III-VI(7) progression, when used as a substitute for I-V-vi?

The bridge goes ii-V / I-V-vi / in the first two lines, then ii-V / I-III-VI(7), resolving to ii-V-I.

I almost feels like a temporary excursion into ii minor or a modal variation, but I'm sure there's a clearer way to explain it.

• Meaning, all major, including VI as a Major 7th chord? – LSM07 May 15 at 22:46

1 Answer

I think this is the chart...

```| ii V | I  V  vi  |
| ii V | I III VI7 |
| ii V | I
```

...I'm not exactly sure of your barlines.

The part `I V vi` can be called a deceptive progression.

The part `I-III-VI(7)` I think you mean in `F` major the chord would be `F A D7`

Functionally I think you could just say `I V/vi V7/ii`. After the tonic chord it's like the beginning of a circle of fifths of dominants. Roots descending by 5th to `ii`. So then the chart could be analyzed like this...

```| ii V | I   V    vi  |
| ii V | I V/vi V7/ii |
| ii V | I
```

In `F` major the named chords are...

```| Gm C | F C Dm |
| Gm C | F A D7 |
| Gm C | F
```

The last five chords are a long segment of the circle of fifths.

We can list out just the roots with Roman numerals and letters...

```F    Bb   E    A    D    G    C    F
I    IV   viio iii  vi   ii   V    I
```

The diatonic chord qualities are...

```F    Bb   Edim Am   Dm   Gm   C    F
I    IV   viio iii  vi   ii   V    I
```

Excepting `IV` and `viio` it totally fine to modify the other chord to become either major triads or dominant seventh chords as long as the function as secondary dominants. I put the sevenths in parenthesis to show it is optional without changing the functional harmony. I also used both kinds of Roman numerals...

```F      Bb     Edim   A(7)   D(7)   G(7)   C(7)   F
I      IV     viio   V/vi   V/ii   V/V    V      I
I      IV     viio   III(7) VI(7)  II(7)  V(7)   I
```

...you can use other combinations of minor chords versus major/dominant sevenths in that part of the circle of fifths from `iii` to `I`. The important thing is the roots descending by perfect fifths.

So, the final part of your piece plays the full circle of fifths using a few secondary domiants but omitting the `IV` and `viio` chords.

• Ha, I should have provided a key. I'm playing it in F, and transposing your comment! – Paul F May 15 at 18:02
• The song is in F. The bridge starts on Gm: Gm C F C Dm Gm C F A D7 Gm C F – Paul F May 15 at 18:06
• sorry, the line breaks didn't hold in that comment – Paul F May 15 at 18:07
• Gm C / F C Dm / Gm C / F A D7 / Gm C / F – Paul F May 15 at 18:08
• @PaulF, I made an edit re. key of F and with the bridge parts. If my bar lines are problematic can you edit your answer to give the exact bars? – Michael Curtis May 15 at 18:38