ground bass
A short bass pattern repeated continuously throughout a composition while upper voices vary freely above it.
In Depth
Ground bass (also called basso ostinato) is a compositional technique where a bass line of typically four to eight measures repeats in an unbroken cycle while the melody, harmony, and texture above it evolve freely. The technique creates a hypnotic effect — the recurring bass provides stability and inevitability while the upper voices generate variety and emotional development against this fixed foundation. The ground bass was a favorite device of Baroque composers, with Purcell's "When I am laid in earth" (Dido's Lament) from Dido and Aeneas being perhaps the most celebrated example. Its five-bar chromatic descending bass line, heard eleven times, becomes increasingly heartbreaking with each repetition. The chaconne and passacaglia are both formal types built on ground bass principles. The technique never disappeared — it underpins blues, jazz, and pop music in the form of repeating chord progressions and bass loops.
Purcell's ground bass in Dido's Lament uses a five-bar phrase rather than the standard four, creating a subtle asymmetry that makes each repetition feel slightly off-balance and more poignant.