In jazz and jazz harmony, the chord progression from iv7 to ♭VII7 to I (the tonic or "home" chord) has been nicknamed the backdoor progression[1][2] or the backdoor ii-V, as described by jazz theorist and author Jerry Coker. This name derives from an assumption that the normal progression to the tonic, the ii-V-I turnaround (ii-V7 to I, see also authentic cadence) is, by inference, the "front door", a metaphor suggesting that this is the main route to the tonic.
The ♭VII7 chord, a pivot chord borrowed from the parallel minor of the current tonic major key, is a dominant seventh. Therefore, it can resolve to I; it is commonly preceded by IV going to iv, then ♭VII7, then I. In C major the dominant would be G7: (the notes GBDF), sharing two common tones with B♭7: (the notes B♭DFA♭). The notes A♭ and F serve as upper leading-tones back to G and E (when the chord moves to the tonic, C major), respectively, rather than B♮ and F serving as the lower and upper leading-tones to C and E in a conventional G7-C major (V7-I) cadence.
A backdoor IV-V is also possible, moving from ♭VIM7 to ♭VII7 to I. This is also commonly known as "Mario Cadence".[3]
- ^ Coker, Jerry (1997). Elements of the Jazz Language for the Developing Improvisor, p.82. ISBN 1-57623-875-X. "Back Door Progression As A Substitute For V7[:] The I chord, in a given progression, is often preceded by IV-7 to ♭VII7, instead of the usual V7 chord.".
- ^ Juusela, Kari (2015). The Berklee Contemporary Dictionary of Music, unpaginated. Hal Leonard. ISBN 9781495028540. "back-door cadence: A IVmi7 ♭VII7 I harmonic cadence."
- ^ Lavengood, Megan (July 1, 2021). "Open Music Theory: Modal Schemas" – via viva.pressbooks.pub.
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