Subdominant

The function

Of the three main functions the subdominant leads away from the tonic and builds up moderate tension, gentler than the dominant. In C major that is F major, in A minor D minor. The basic movement of harmony T–S–D–T forms the cadence. The subdominant parallel (Sp in German functional theory), the relative chord on degree ii, takes the place of the subdominant. The progression ii–V–I is everywhere in jazz.

Plagal cadence and half cadence

The plagal cadence leads from the subdominant to the tonic, in major IV–I, in minor iv–i. It sounds softer and more solemn than the authentic cadence, without the pressing leading tone. Because it is so often used at the end of chorales, it is also called the “Amen cadence”. If a phrase ends with IV–V instead, it stays open: the half cadence. In its minor form the subdominant can also appear in major as a borrowed chord: in C major that is Fm. The page on the circle of fifths names this modal borrowing and describes the sound as bittersweet.

The pop pattern I–V–vi–IV has the subdominant at the end. In C major that is C–G–Am–F. On the circle of fifths tonic, subdominant and dominant lie directly next to each other.

Common mistakes

• Swapping subdominant and dominant: IV is the fourth above the tonic, V the fifth.
• Calling a plagal cadence an authentic cadence: The leading tone is missing.
• Taking the minor subdominant in major for a mistake: As a borrowed chord it is a deliberate stylistic device.