BVII-I cadence

Subtonic

In music, the subtonic or flattened seventh (♭VII) is the lowered or minor seventh degree of the scale, a whole step below the tonic, as opposed to the leading tone. The subtonic appears in three forms: as the scale degree, ♭, melodically and as the chord ♭VII in both ♭VII-I cadence and in modulations harmonically.

For example, in the A minor scale (white keys on a piano, starting on A), the subtonic is the note G (in C major this would be B♭); and the subtonic chord uses the notes G, B, and D (in C: B♭-D-F). In music theory, the subtonic chord is symbolized with the Roman numeral ♭VII for a major triad built on the note, or ♭vii for a minor triad; in a minor key, the flat symbol is sometimes omitted by some theorists because the subtonic note appears in the natural minor scale, but the flat symbol is usually used for the major scale because the subtonic is a non-scale note.

In jazz, the flattened seventh is also used as a substitute for the dominant, V, especially in the Backdoor cadence, ii-♭VII7-I, where the subtonic is used for the dominant seventh. ♭VII is in this case a pivot chord borrowed from the parallel minor (its dominant seventh). V7 and ♭VII7 have two common tones, in C: GBDF and B♭DFA♭.

In classical music, use of the subtonic is generally rare in major keys apart from reference to the subdominant key (one less sharp or one more flat), but the subtonic chord is considered diatonic in a minor key. Minor key non-classical music has seen most of the use of the subtonic. It often functions as an alternate to a minor dominant chord, and is often led into and out of the tonic chord. Modulation to the subtonic is relatively rare, compared with, say, modulation into the dominant (see: closely related key).

However, even in a minor key, use of the subtonic, while implied in some pre-Baroque music due to the use of "minor-sounding" musical modes, was never popular in much of traditional classical music, apart from references to the relative major key, since the subtonic is the dominant of the relative major.

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 (ie, ♮-) is often absent. In popular music, rather than, "departures," or, "aberrant," the, "use of the 'flattened' diatonic seventh scale degree...should not even be viewed as departures".

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