Thoroughbass

Thoroughbass, also known as figured bass, is a system of musical notation used in the Baroque era to indicate harmonic structure beneath a bass line. In a thoroughbass part, the bass line is written in the lowest staff, often with numeral figures placed above or below the notes to show the intervals that should be supplied above the bass. The figures guide the continuo players—typically a keyboard instrument such as a harpsichord or organ, often supported by a bass instrument (cello, viol, bass viol)—in realizing a chordal accompaniment.

The practice originated in 16th- and 17th-century Italian music and became standard in Baroque ensembles. Composers such as J.S. Bach, G. F. Handel, Arcangelo Corelli, and Antonio Vivaldi wrote continuo parts that depended on figured bass realizations. The numbers represent intervals above the bass note; a 5-3 chord signifies a basic triad in root position, a 6 indicates a first inversion triad, and a 6-4 form often signals cadential or suspended harmony. Realization was not fixed; performers add appropriate chord tones and voice-leading to fit the style and tempo of the piece.

Although the term thoroughbass is commonly used in historical literature, it is largely synonymous with figured bass in modern scholarship. The concept remains central to the understanding of continuo performance and Baroque harmonic practice.