Leading chords
Dissonant chords (e.g. seventh chord, diminished triad) that require resolution to a consonant sonority.
What it means
Leading chords are chords whose dissonant make-up gives them a strong tendency to resolve to a consonant sonority. The most important examples are the dominant seventh chord and the diminished triad, whose dissonances (a minor seventh and a diminished fifth respectively) are led, by traditional voice-leading rules, stepwise into a stable target chord.
The term thus describes a function more than a fixed chord type: leading chords drive a cadence or phrase forward by creating tension that demands release.
Musical use
In classical harmony, leading chords are a central means of preparing a target sonority such as the tonic; the resolution of the dominant seventh chord to the tonic is the best-known example. Leading chords should be distinguished from mere passing chords, which lack such a strong pull towards resolution, and from stable, consonant sonorities such as the plain triad, which itself demands no resolution.
Performance practice
Listen consciously for the tension of a leading chord and shape the following resolution as an audible goal, for instance with a slight easing of dynamics once the consonant sonority is reached.