ground bass explained
A short bass pattern repeated throughout a composition while the upper voices vary freely above it
In Depth
Ground bass (or basso ostinato) is one of the oldest and most powerful compositional techniques. The bass pattern — typically four to eight bars — provides a fixed harmonic foundation over which the upper voices develop, vary, and intensify with each repetition. Purcell's Dido's Lament is built over a chromatically descending ground bass that is repeated eleven times, each repetition increasing the emotional intensity. The technique was central to Baroque passacaglias and chaconnes.
Purcell's Dido's Lament uses a five-bar ground bass rather than the conventional four or eight bars, creating a phrase overlap that heightens the sense of emotional disorientation.