Leading tone

In music theory, a leading tone (also called subsemitone or leading note in the UK) is a note or pitch which resolves or "leads" to a note one semitone higher or lower, being a lower and upper leading tone, respectively. Typically, the leading tone refers to the seventh scale degree of a major scale (), a major seventh above the tonic. In the movable do solfège system, the leading tone is sung as si.

A leading-tone triad is a triad built on the seventh scale degree in a major key (viio in Roman numeral analysis), while a leading-tone seventh chord is a seventh chord built on the seventh scale degree (viiø7). Walter Piston considers and notates viio as V07, an incomplete dominant seventh chord. (For the Roman numeral notation of these chords, see Roman numeral analysis.)

Note

Seventh scale degree (or lower leading tone)

Typically, when people speak of the leading tone, they mean the seventh scale degree () of the major scale, which has a strong affinity for and leads melodically to the tonic. It is sung as si in movable-do solfège. For example, in the F major scale, the leading note is the note E.

As a diatonic function, the leading tone is the seventh scale degree of any diatonic scale when the distance between it and the tonic is a single semitone. In diatonic scales in which there is a whole tone between the seventh scale degree and the tonic, such as the Mixolydian mode, the seventh degree is called the subtonic. However, in modes without a leading tone, such as Dorian and Mixolydian, a raised seventh is often featured during cadences, such as in the harmonic minor scale.