Backdoor progression

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 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♭).