Definition
The backdoor progression ("through the service door") is ivm7 – bVII7 – I: in C, Fm7 – Bb7 – Cmaj7. The name, attributed to the educator Jerry Coker, sets it against the ii–V–I, the "front door" to the tonic. Both chords come from the parallel minor (C minor): it is a case of modal interchange with the function of minor subdominant.
Why it resolves
- Bb7 (Bb D F Ab) shares D and F with G7 (G B D F): it has half the "body" of the dominant.
- Ab → G (b6 → 5) and F → E (4 → 3) are half-step motions toward the tonic triad; Bb → C rises by a whole step, D rises to E or falls to C.
- The leading tone B is missing: the resolution is soft, warm, "nostalgic," closer to the plagal cadence than to the authentic one.
- In negative harmony Bb7 is the image of Bø7 (the leading-tone seventh chord): a "dominant from below."
Variants
| Variant | Chords in C | Degrees |
|---|---|---|
| Full backdoor | Fm7 Bb7 Cmaj7 | ivm7 bVII7 Imaj7 |
| Backdoor dominant only | Bb7 Cmaj7 | bVII7 Imaj7 |
| With iv6 | Fm6 Bb7 C | iv6 bVII7 I |
| Backdoor IV–V ("Mario cadence") | Ab Bb C | bVI bVII I |
| Front door + backdoor | Dm7 G7 / Fm7 Bb7 / C | double path to I |
| Backdoor in minor | Fm7 Bb7 Ebmaj7 | the bVII7 as V of bIII |
On the bVII7 the typical scale is Lydian dominant (Bb C D E F G Ab), which contains E and therefore "anticipates" the major tonic; Mixolydian (with Eb) sounds bluesier.
Real examples
- Misty (Erroll Garner, Eb): | Ebmaj7 | Bbm7 Eb7 | Abmaj7 | Abm7 Db7 | Ebmaj7 … The Abm7 – Db7 in bars 4–5 is an ivm7 – bVII7 that returns to Eb.
- Lady Bird (Tadd Dameron, C): Cmaj7 for two bars, then Fm7 – Bb7 – Cmaj7; later the same movement returns, and the tune closes with the famous turnaround Cmaj7 – Ebmaj7 – Abmaj7 – Dbmaj7.
- Pop, gospel, and soul very often use just the bVII → I (even in triads: Bb → C) as a "rock" cadence.
Practical use
- In place of a final ii–V for a gentler ending (ballad, soundtrack).
- As a second turnaround in a tune that has already used the ii–V a lot: it varies the color without changing the form.
- In pop bridges: IV – iv – bVII7 – I (F – Fm – Bb7 – C) creates a melancholic descent toward the chorus.
Voice leading (4-part voicing)
- Fm7: Ab – C – Eb – F
- Bb7: Ab – D – F – Bb (or Ab – C – D – F with the ninth)
- Cmaj7: G – B – E – G (or G – C – E – B)
The Ab voice falls to G, Eb rises to E (through D or directly), F falls to E: all by half step.
Exercise for the producer
- 4-bar loop in C: Cmaj7 – Am7 – Dm7 – G7.
- On the repeat, replace the last two bars with Fm7 – Bb7.
- Mix a Rhodes (Stage-73 V) with slow tremolo: compare the sense of arrival in the two versions.
- Also try Ab – Bb – C with synth brass for a "video game" ending.
Related topics
Modal interchange, plagal cadence and minor plagal, negative harmony (applications), related ii–V, jazz harmonic analysis.