The backdoor progression and other wizardry

[Jean-Michel G]

Tonal music is all about cadences: those very specific chord sequences that constitute the harmonic signatures of the songs.
The best known of them revolve around the V chord: V – I, IV – V – I, IV – V, ii – V – I, etc.

But pop and rock are not so fond of V – I or ii – V – I cadences, although you do find them. You will probably find more IV – I cadences (“plagal cadence”), which is also a staple of the blues.

Another very frequent cadence in pop and rock is the bVII7 – I cadence, sometimes called the “backdoor cadence” or “backdoor progression”.
It appears in numerous songs, for example: SOS (Abba), Lady Madonna (Beatles), Summer Of 69 (Bryan Adams), Bold As Love (Hendrix), etc.

In C major, that would be Bb7 – C.
The bVII7 is often preceded by a iv or iv7 chord, like so: Fm7 – Bb7 – C.
This is interesting, because Fm7 – Bb7 is a ii7 – V7 in Eb major, but instead of resolving to the expected I (Eb), it resolves to C…

Technically, the bVII7 is a borrowed chord from the parallel minor mode.
The primary reason why this cadence works is because of the voice leading; for example in C major, the progression is Fm7 – Bb7 – C6; let’s voice them in root position for example:
Fm7 = (F Ab C Eb)
Bb7 = (Bb D F Ab) = (F Ab Bb D)
C6 = (C E G A) = (E G A C)
You can easily see how the four chord voices progress to the resolution chord.

But there is more…

Let’s start with a Bdim7 chord: (B D F Ab).
As you know, this chord happily resolves to C or Cm because it has the same tritone (B F) as G7 and Bm7(b5). It also resolves to Eb or Ebm because of the tritone (D Ab).

But the magical thing about dim7 chords is, that you can flatten any of its chord tones to obtain a chord that also happily resolves to C!
For example, with Bdim7:
– flattening the Ab -> (B D F G) = G7 -> C (the authentic cadence)
– flattening the B -> (Bb D F Ab) = Bb7 -> C (the backdoor cadence)
– flattening the D -> (B Db F Ab) = Db7 -> C (Db7 is a tritone substitution of G7)
– flattening the F -> (B D E Ab/G#) = E7 -> C (subtle but effective)
As you can see, flattening any chord tone of a dim7 chord produces a dominant 7th chord that you can use to resolve to a major or minor chord a semitone above the dim7 root.

You can also sharpen any chord tone of the dim7 chord and obtain a chord that still resolves happily to a chord a semitone above the dim7 root.
For Bdim7:
– sharpening the Ab -> (B D F A) = Bm7(b5) -> C
– sharpening the D -> (B D#/Eb F Ab) = Fm7(b5) -> C
– sharpening the F -> (B D F#/Gb Ab) = Abm7(b5) -> C
– sharpening the B -> (C D F Ab) = Dm7(b5) -> C
As you can see, sharpening any chord tone produces a half-diminished chord.

So, in summary, all the following chords can be used to resolve to C: Bdim7, G7, Bb7, Db7, E7, Bm7(b5), Fm7(b5), Abm7(b5), Dm7(b5)!
All these chords result from the alteration of the Bdim7 chord!

If you wanted to resolve to A, all you would have to do is take the G#dim7 chord (or Abdim7 if you prefer) and alter it the way I did above. That would give you eight additional possibilities to resolve to A.
Also remember that any voicing of a dim7 chord repeats itself every three frets on a guitar; that makes it easy to visually use the trick above.

Have fun!

[charjo]

J-M,
I suspect this contains a lot of what I’ll need to really understand diminished chords and tritone substitutuions. I need to sit with my guitar and ponder all of this. Thank you for this great overview.
John

[Ralph P.]

Thanks for the theory behind the diminished chord resolving to the chord a step above, it. I’ve used that move in 3 or 4 songs that I’ve written (resolving to both major and minor chords), and never knew the theory behind it. I just knew it sounded good. Now I know why. Got the diminished thing from George Harrison. He was very fond of diminished chords.

I’ll have to try sharpening and flattening one of the notes next time I use a diminished chord. Very interesting and useful knowledge.

As you mentioned, I learned many years ago that diminished chords repeat every 3 frets, which I thought was so cool. Makes them very accessible and easy to find.

Thanks for the insights,
Ralph

Ralph P.

[Ralph P.]

As for the “backdoor progression, I find it much more common to have a bVII instead of bVII7th. The bVII is straight out of the Mixolydian scale. I can’t really think of any songs that use a bVII7th, although they are probably out there. The regular major chord bVII is all over Rock and Country and Blues music.

I like the term “backdoor progression”. Sounds so Rock N’ Roll.

Ralph

Ralph P.

[Author]

Posts