bVII7I

bVII7I refers to a harmonic progression in which a dominant seventh chord built on the lowered seventh scale degree (the subtonic) moves to the tonic in a major key. This is a form of modal mixture, borrowing chords from the Mixolydian mode or the parallel minor to create a chromatic color that contrasts with strictly diatonic harmony.

Construction and examples: In a major key, the bVII7 chord is built on scale degree b7. For example, in C major the bVII7 is Bb7 (Bb-D-F-Ab). A common following chord is I, so a typical progression is Bb7 to C major. In G major, the bVII7 would be F7 (F-A-C-Eb) resolving to G major. The chord is described as a dominant seventh, but it is not the diatonic V7 of I; instead it functions as a borrowed, pre-dominant-like color that strongly leads toward the tonic.

Function and usage: The bVII7I progression is especially common in rock, pop, blues, and jazz-inflected styles, where it provides a bluesy, modal flavor and a clear, decisive pull back to the tonic. It can serve as a pre-dominant or as a coloristic substitute for other voice-leading paths. The seventh of the chord (the flat seventh of the key) is often retained for its strong, characteristic sound, though in some arrangements the seventh may be omitted.

Notes: The concept generalizes across keys; in minor keys, the same idea appears with the appropriate lowered scale degree producing a dominant seventh that resolves to i. The bVII7 chord is also known as the subtonic seventh and is a common example of borrowed harmony in tonal music.