Inmusic, thesubtonic is the degree of a musical scale which is awhole step below thetonic note. In amajor key, it is a lowered, or flattened, seventhscale degree (♭). It appears as the seventh scale degree in thenatural minor anddescending melodic minor scales but not in themajor scale. In major keys, the subtonic sometimes appears inborrowed chords. In themovable do solfège system, the subtonic note is sung aste (orta).

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The scale and subtonic triad in C minor.

The subtonic can be contrasted with theleading note, which is ahalf step below the tonic.^[1] The distinction between leading note and subtonic has been made by theorists since at least the second quarter of the 20th century.^[2] Before that, the termsubtonic often referred to the leading tone triad, for example.^{[3][4][5][6][7]}

The wordsubtonic is also used as an English translation ofsubtonium, the Latin term used inGregorian chant theory for the similar usage of a tone one whole step below the mode final in theDorian,Phrygian, andMixolydian modes.^[8]

Thetriad built on the subtonic note is called the subtonic chord. InRoman numeral analysis, the subtonic chord is symbolized by the Roman numeral "♭VII" in a major key. In a minor key, it is often written as "VII", theflat symbol being often omitted by some theorists because the subtonic note appears in the natural minor scale. The flat symbol is used for the major scale because the subtonic is a non-diatonic note.

TheoristsStefan Kostka and Dorothy Payne describe the subtonic chord (VII) as "sounding like the V in the key of therelative major—that is, aV of♭III."^[10]Allen Forte writes that "[w]hile VII in relation to C minor (I) becomes V in relation to III (E♭ major).... As a major triad on an unaltered or natural scale degree 7 in minor the VII functions as a secondary dominant triad in relation to the mediant."^[9] In the minor mode, the subtonic chord may also appear as amajor minor seventh chord (i.e. dominant seventh chord),♭VII⁷.^[11]

Injazz, the flattened seventh is also used as asubstitute for thedominant, V, especially in thebackdoor cadence,^[12] ii–♭VII⁷–I, where the subtonic is substituted for the dominant seventh. In this case,♭VII functions as apivot chord borrowed from theparallel minor (its dominant seventh). The chords V⁷ and♭VII⁷ have twocommon tones: in C major, these chords are G–B–D–F and B♭–D–F–A♭.

However, while "the leading-tone/tonic relationship is axiomatic to the definition ofcommon practice tonality", especiallycadences andmodulations, inpopular music androck a diatonic scalic leading tone (i.e.,♮ – ) is often absent.^[13] In popular music, rather than "departures" or "aberrant", the "use of the 'flattened' diatonic seventh scale degree… should not even be viewed asdepartures".^[14] In reference to chords built on the flattened seventh,Richard Franko Goldman argues that "the concept ofborrowing is in actuality unnecessary. The mixture of major and minor is a simple fact in theClassical andRomantic periods."^[15]

• ♭VII–V⁷ cadence
• Leading note

Sources

• Moore, Allan F. (1995). "The So-called 'Flattened Seventh' in Rock".Popular Music.14 (2):185–201.doi:10.1017/S0261143000007431.S2CID 162661553.

• Stell, Jason Travis. 2006. "The Flat-7th Degree in Tonal Music". PhD diss. Princeton: Princeton University.