Subdominant

What it means

The subdominant is the fourth degree of a key and the triad built on it, in function theory S (IV). It is one of the three main functions. Its name — the “lower dominant” — describes its position: it lies a fifth below the tonic, just as the dominant lies a fifth above it.

Musical use

In the cadence T–S–D–T (I–IV–V–I), the subdominant leads away from the tonic and prepares the dominant. It thus forms the counter-pole to the dominant: this strives toward the tonic, that opens away from it. Its sound correspondingly seems relaxed and expanding, without the pressing tension of the dominant.

The most important note is the fourth degree itself, which, as the root of the subdominant, lies a semitone above the third of the tonic and presses downward toward it. In the dominant seventh, the same note reappears, which explains the kinship of the two functions.

The subdominant has several representatives. The subdominant's relative on the second degree is often used in cadences in place of the subdominant and sounds softer. The subdominant with an added sixth reinforces its character. The Neapolitan sixth chord is an altered form with a lowered second degree. In minor the subdominant is a minor sonority; in major, the minor subdominant occasionally appears as a change of colour.

The direct connection S–T without a dominant yields the plagal cadence, known as the Amen cadence.

The subdominant lies a fifth below the tonic and forms, with the dominant, the counter-pair of the cadence. In the plagal close it leads directly to the tonic. In function theory it is called S, in minor s. Its relative is Sp, its counter-chord Sg. In English it is called subdominant.

Performance practice

Shape the subdominant as an opening, not as a goal — it leads onward. Watch the fourth degree in the melody, which presses downward to the third. And listen to the difference between the subdominant and its relative; it colours the cadence and wants to be shaped deliberately.