In music, the dominant is the fifth degree of the scale. For example, in the C major scale (white keys on a piano, starting with C), the dominant is the note G; and the dominant chord uses the notes G, B, and D. In music theory, the dominant chord is symbolized by the Roman numeral V if it is within the major mode (because it is a major triad, for example G-B-D in C major) or v if it is within the minor mode (because it is a minor triad, for example G-B♭-D in C minor, unless of course the B♭ is sharpened to B natural, as will often occur since B natural is the leading tone for the C minor scale). As defined by Joseph Fétis the dominante was a seventh chord over the first note of a descending perfect fifth in the basse fondamentale or root progression, the common practice period dominant seventh he named the dominante tonique. A cadential dominant chord followed by a tonic chord (the chord of the key of the piece) produces an authentic cadence. If the roots are in the bass and the tonic is in the highest voice, it is a perfect authentic cadence. "Dominant" also refers to a relationship of musical keys. For example, relative to the key of C major, the key of G major is the dominant. Music which modulates (changes key) often modulates into the dominant. Modulation into the dominant key often creates a sense of increased tension; as opposed to modulation into subdominant (fourth note of the scale), which creates a sense of musical relaxation (because the tonic key is the dominant of its subdominant key: in F major, the dominant is C). The dominantdiatonic function has the role of creating instability that requires the tonic or goal-tone for release. The dominant may also be considered the result of a transformational operation applied to the tonic that most closely resembles the tonic by some clear-cut criteria such as common tones (Perle 1955 cited in Wilson 1992, p.37-38).
Dahlhaus, Carl. Gjerdingen, Robert O. trans. (1990). Studies in the Origin of Harmonic Tonality, p.143. Princeton University Press. ISBN 0-691-09135-8.
