The Minor iv

A minor chord on the fourth degree of a key whose home chord is major. One note gives it away — the key’s lowered sixth — and the reader finds it by that note.

The rule, as the reader applies it

  1. In a key whose tonic chord is major: a minor chord a fourth above the tonic, with at least one note outside the key.

Where it fires: one time in one line

Every line in this site’s corpus where the minor iv 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 F Fm C C major Fm iv constructed test case

The move as declared here was read from Borrowed chord, “Common borrowed chords” (Wikipedia), which prints it as iv in C major: F–Ab–C.

Spotting it

The reader flags a minor iv from three facts about one chord, read in the key the line settles in. Its root sits a fourth above the tonic; its triad is minor; and at least one of its notes lies outside the key. The key's own tonic chord must be major, too. In C major the chord is F minor, and the note that gives it away is Ab: the key holds A, and the chord holds the note a semitone below it.

In the table

The row's numeral is iv, lower case because the chord is minor, and the fit column names Ab as the note outside the key. A major IV in the same line reads IV with nothing outside it, so a line that holds both, such as C F Fm C, puts the two chords side by side and the single changed note is the whole difference between their rows. A seventh does not hide the move: C Fm7 C is flagged the same way, and so is a chord over a different bass note, as in C F/A Fm/Ab C/G, because the degree is counted from the root of the chord, not its lowest note.

What is not flagged

In a minor key the minor chord on the fourth degree is the key's own iv. Am Dm Am reads in A minor with Dm as iv and nothing outside the key, and the move does not fire, because the rule only applies where the tonic chord is major.

With a tie

Short lines often tie between a major key and another mode on the same tonic. The move is flagged in whichever tied key the page reads in, as long as that key's tonic chord is major and one of the chord's notes falls outside it, and the tie buttons above the table re-read the line in each of the others.