Backdoor progression


In jazz and jazz harmony, the chord progression from iv7 to VII7 to I has been nicknamed the backdoor progression 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 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:, sharing two common tones with B7:. The notes A and F serve as upper leading-tones back to G and E, respectively, rather than B and F serving as the lower and upper leading-tones to C and E in a conventional G7-C major cadence.

Alternative usage

The term "Backdoor" has been used by author Shelton Berg to refer to another entirely unrelated progression. The unexpected modulation created through the substitution of the highly similar Imaj9 for iii7 at the end of the ii7-V7 turnaround to a tonicized iii, arrives at 'home' through unexpected means, the 'back door' instead of the 'front door'. The resolution of a dominant seventh chord up a step is called a deceptive cadence.