Scales, Keys & Modes

Subtonic

Pronounced sub-TON-ik

Definition

The subtonic is the seventh degree of a scale when it lies a whole step below the tonic, as G does in A natural minor. Unlike the leading tone, it has little pull toward the tonic.

The subtonic is scale degree 7 when it sits a whole step below the tonic. It is the normal 7th degree of the natural minor scale (G in A minor) and of the Mixolydian mode (F in G Mixolydian), and it is the note musicians mean when they talk about a "flat seven", such as B♭ in C.

Two treble-clef examples in 4/4. A natural minor: quarter notes A B C D E F G A, numbered 1 to 8, with the word subtonic written under G. C Mixolydian: C D E F G A B-flat C, numbered 1 to 8 with flat 7 under B-flat, and subtonic under B-flat. — The subtonic is a 7th degree a whole step below the tonic: G in A natural minor, and B♭ in C Mixolydian (or in C major when a ♭7 is borrowed).

Subtonic or leading tone?

Both names belong to the 7th degree; the distance to the tonic decides which one applies. A half step below the tonic, the 7th is the leading tone, and it pulls hard upward. A whole step below, it is the subtonic, and most of that pull disappears. Compare the two in A minor:

Two grand-staff examples in 4/4, two bars each, with chord symbols. Both start with right-hand quarter notes E D C B over an A minor chord. The first ends A, G, half-note A over chords Am, G, Am. The second ends A, G-sharp, half-note A over chords Am, E, Am. — The same original phrase in A minor with two different 7ths. With G, the subtonic, harmonized by a G major chord, the return to A is gentle. With G♯, the leading tone, harmonized by E major, the pull to A is strong.

With G♯ the line sounds as if it must go to A. With G it can rise to A, but it could just as easily turn back down; the phrase feels relaxed and modal, closer to folk music than to a classical cadence.

The subtonic chord

The triad on the subtonic is major: G B D in A natural minor, or B♭ D F borrowed into C major. In rock and pop analysis it is written ♭VII. Its move to the tonic chord, ♭VII–i or ♭VII–I, is one of the defining sounds of rock and pop: it reaches home by step without any leading tone. Progressions such as i–♭VI–♭VII–i in minor and I–♭VII–IV–I in major are built around it.

In classical minor-key music, the subtonic chord (written VII) usually appears on its way somewhere else, most often as the dominant of the relative major: G major leading to C major in A minor.

Spotting it

In a major key, a lowered 7th written as an accidental (B♭ in C major) is a borrowed subtonic, often a sign of the Mixolydian mode or of a borrowed chord from the parallel minor. In a minor key, a 7th degree without the raising accidental is the subtonic; with it, the leading tone. The three minors shows both, and Minor-Key Chords: Natural or Raised Seventh? asks you to tell them apart.

Common questions

What is a ♭VII chord?

The major triad built on the subtonic: G major in A minor, or B♭ major borrowed into C major. It often moves straight to the tonic chord, a common ending in rock and pop.

Does a major key have a subtonic?

Not in its own scale: the 7th degree of a major scale is a leading tone. A lowered 7th in a major key, such as B♭ in C major, is borrowed from the parallel minor or the Mixolydian mode.