Backdoor progression

In jazz and jazz harmony, the chord progression from ii⁷ or 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 (ii-V⁷ to I, see also authentic cadence) is, by inference, the front door. It can be considered a minor plagal cadence in traditional theory (see modal interchange and plagal cadence).

The backdoor progression can be found in popular jazz standards in such places as measures 7 and 8 of the A section of "Cherokee," measures 9 and 11 of "My Romance" or measures 10 and 28 of "There Will Never Be Another You," as well as Beatles songs like "In My Life" and "If I Fell."

The ♭VII⁷ chord, a pivot chord borrowed from the parallel minor of the current 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: GBDF, sharing two common tones with B♭⁷: B♭DFA♭. 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.

The term "Backdoor" has been used by author Shelton Berg to refer another entirely unrelated progression. The unexpected modulation created through the substitution of the highly similar I^maj9 for iii⁷ (in C: CEGBD and EGBD) at the end of the ii^ø7-V⁷ turnaround to iii (ii^ø7/iii=♯iv^ø7, V⁷/iii=VII⁷, iii), arrives at 'home' (the tonic) through unexpected means, the 'back' instead of the 'front door'(iii⁷, EGBD, being entirely contained within I^maj9, CEGBD, and the seventh still resolving downward). The resolution of a dominant seventh chord up a step (in this case a half-step) is called a deceptive cadence.