What is a ground bass and how did Henry Purcell use it?

A ground bass is a short, recurring melodic pattern in the bass part of a musical composition that serves as the primary structural foundation. During the Baroque era, this technique—also known as basso ostinato—was frequently used to create continuous variations, where new melodies were composed or improvised above the repeating bass line.1

Henry Purcell masterfully employed the ground bass to provide emotional and structural depth to his works. His most famous application of this technique is the aria "When I Am Laid in Earth" from his opera Dido and Aeneas (1689). In this piece, the persistent, repeating bass pattern anchors the vocal melody, heightening the sense of lament and inevitability as the character faces her fate. By utilizing the ground bass, Purcell demonstrated how a rigid, repetitive structure could be transformed into a powerful vehicle for expressive, dramatic storytelling.1