In music, the subtonic is the flattened seventh scale degree (♭) of the diatonic scale, that is, the lowered or minor seventh degree of the scale, a whole step below the tonic. In the movable do solfège system, the subtonic note is sung as te (or ta). It appears in the natural minor and descending melodic minor scales but not in the major scale. In major keys, the subtonic sometimes appears in borrowed chords.
The subtonic can be contrasted with the leading tone, which is a half step below the tonic. The distinction between leading tone and subtonic has been made by theorists since at least the second quarter of the 20th century. Before that, the subtonic often referred to the leading tone triad, for example.
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.
The triad built on the subtonic note is called the subtonic chord. In Roman numeral analysis, the subtonic chord is symbolized by the Roman numeral "♭VII". 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-diatonic note.
Theorists Stefan Kostka and Dorothy Payne describe the subtonic VII as "sounding like the V in the key of the relative major—that is, a V of ♭III." 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." In the minor mode, the subtonic chord may also appear as a major minor seventh chord (i.e. dominant seventh chord), ♭VII7.
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 substituted for the dominant seventh. In this case, ♭VII functions as a pivot chord borrowed from the parallel minor (its dominant seventh). The chords V7 and ♭VII7 have two common 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 of common practice tonality", especially cadences and modulations, in popular music and rock a diatonic scalic leading tone (i.e., ♮–) 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". In reference to chords built on the flattened seventh, Richard Franko Goldman argues that "the concept of borrowing is in actuality unnecessary. The mixture of major and minor is a simple fact in the Classical and Romantic periods."
- Bruce Benward and Marilyn Nadine Saker, Music: In Theory and Practice, vol. 1, seventh edition (Boston: McGraw-Hill, 2003), p. 33. ISBN 978-0-07-294262-0. "Used only to designate the seventh degree of the natural minor scale."
- Donald Tweedy, Manual of Harmonic Technique Based on the Practice of J. S. Bach (Philadelphia: Oliver Ditson Company, 1928), p. 7.
- Herbert, John Bunyan (1897). Herbert's Harmony and Composition, p. 102. Pennsylvania State. [ISBN unspecified]
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- Root, George Frederick (1872). The Normal Musical Hand-book, p. 315. J. Church. [ISBN unspecified] "The name in harmony sometimes given to seven of a diatonic scale," p. 344.
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- Julian Rushton, "Subtonic", The New Grove Dictionary of Music and Musicians, second edition, edited by Stanley Sadie and John Tyrrell (London: Macmillan Publishers, 2001); Harold C. Powers, "Subtonium", The New Grove Dictionary of Music and Musicians, second edition, edited by Stanley Sadie and John Tyrrell (London: Macmillan Publishers, 2001)
- Forte, Allen, Tonal Harmony, third edition (S.l.: Holt, Rinehart, and Wilson, 1979): p. 116 and 123. ISBN 0-03-020756-8.
- Kostka, Stefan and Payne, Dorothy (1995). Tonal Harmony, p. 118. McGraw Hill. ISBN 0-07-035874-5.
- Kostka, Stefan; Payne, Dorothy (2004). Tonal Harmony (5th ed.). Boston: McGraw-Hill. p. 220. ISBN 0072852607. OCLC 51613969.
- Jerry Coker, Elements of the Jazz Language for the Developing Improvisor (Miami: CCP/Belwin, Inc, 1991), p. 82. ISBN 1-57623-875-X.
- Moore 1995, p. 187.
- Moore 1995, p. 186.
- Goldman, Richard Franko (1965). Harmony in Western Music, p. 76. Barrie & Jenkins/W.W. Norton. ISBN 0-214-66680-8.
- Stell, Jason Travis. 2006. "The Flat-7th Degree in Tonal Music". PhD diss. Princeton: Princeton University.