V of vi

A major chord or dominant seventh on the third degree of a major key, followed by the minor chord on the sixth. The raised fifth of the key inside it is what the reader sees first.

The rule, as the reader applies it

  1. In a key whose tonic chord is major: a major chord (a triad or a dominant seventh) a major third above the tonic, with at least one note outside the key, followed by a minor chord a major sixth above the tonic.

Where it fires: one time in one line

Every line in this site’s corpus where V of vi fires: the line, the key it is read in, the chords the move covers and their numerals.
Line Read in Chords Numerals Line from
C E7 Am F G C C major E7 Am III7–vi constructed test case

The move as declared here was read from Secondary chord, “In jazz and popular music” (Wikipedia), which prints it as V/vi in C major: E (E–G#–B) leading to Am.

Spotting it

The reader needs two chords. The first is a major triad or a dominant seventh whose root sits a major third above the tonic of a major key, with at least one note outside that key; the second is the minor chord on the sixth degree. In C major that is E or E7 followed by A minor. The note outside the key is G#, which the fit column names on the first chord's row.

In the table

In C E7 Am F G C the E7's numeral is III7 and the Am after it reads vi. The label sits on the E7, and the span covers both chords, because the rule is about where the first chord goes.

Or a chromatic mediant

The same chord can be two different moves, and what follows it in the line decides which. E major a third above C major, with the tonic's own quality, is the shape of a chromatic mediant, and the source for that move names III as V/vi in so many words. The reader checks the chord after it. When it is the minor vi, the E leans on it and the reader calls it V of vi, and the chromatic mediant rule, which refuses a chord whose root falls a fifth to the next one, stays silent. When the E goes back to the tonic, as in C E C, nothing is being leaned on, V of vi does not fire, and the reader calls the E a chromatic mediant instead. C E7 F C is the same: the E7 goes to F, not A minor.

Major keys only

The rule asks for a major tonic chord and a minor vi. In a minor key the chord a major third above the tonic has a different job, and the rule does not look for it there.