[3][4][5][6][7] The word subtonic is also used as an English translation of subtonium, the Latin term used in Gregorian chant theory for the similar usage of a tone one whole step below the mode final in the Dorian, Phrygian, and Mixolydian modes.
Theorists Stefan Kostka and Dorothy Payne describe the subtonic chord (VII) as "sounding like the V in the key of the relative major—that is, a V of ♭III.
In this case, ♭VII functions as a pivot chord borrowed from the parallel minor (its dominant seventh).
However, while "the leading-tone/tonic relationship is axiomatic to the definition of common practice tonality", especially cadences and modulations, in popular music and rock a diatonic scalic leading tone (i.e., ♮–) is often absent.
[14] In reference to chords built on the flattened seventh, Richard Franko Goldman argues that "the concept of borrowing is in actuality unnecessary.