Dominant
The fifth degree and principal sonority leading to the tonic.
What it means
The dominant is the fifth degree of a key and the triad built on it, in functional theory D (V). It is one of the three principal functions and the one that aims most strongly at the tonic. Its name — the “ruling” one — describes its position: no other sonority determines the key as unambiguously as the path from the dominant to the tonic.
Musical use
Its directing force rests on the leading tone, the third of the dominant triad, which lies a semitone below the root of the tonic and strives upward. With an added minor seventh the dominant becomes the V7 (German D7), and between third and seventh the tritone arises, whose resolution carries the cadence. In minor the dominant is by nature a minor sonority without a leading tone; for the cadence the seventh degree is raised so that it becomes a major sonority.
The dominant is the starting point of the most important cadences: the authentic cadence leads from it to the tonic, the half cadence stops on it, the deceptive cadence leads from it to a substitute for the tonic. It is often delayed by a cadential six-four chord, which is interpreted as a dominant with a double suspension.
The principle can be transferred to every degree: a dominant that relates to a degree other than the tonic is called a secondary dominant. The dominant of the dominant is called the double dominant. In formal construction, the dominant key is the preferred goal of modulations in major pieces.
In the functional system the dominant stands opposite the subdominant; both are related by a fifth to the tonic. The dominant contains the leading tone, which prepares the return to the tonic. That is why it is especially suited to half cadences, build-up of tension, and long pedal points before the recapitulation. The dominant of the dominant is called the double dominant.
Performance practice
Give the dominant tension and direction — it is not the goal but the way. Lead the leading tone upward and intonate it close. And when working up a piece, listen deliberately to the dominant sonorities: they tell you where the music wants to go.