basso continuo
A form of musical accompaniment in Baroque music where a bass line is played by a low instrument while a keyboard or lute fills in the harmonies from figured bass notation.
In Depth
Basso continuo (Italian for "continuous bass"), often simply called "continuo," was the harmonic backbone of virtually all Baroque music from roughly 1600 to 1750. The system required at least two performers: a bass-line instrument (cello, viola da gamba, or bassoon) playing the written bass notes, and a chordal instrument (harpsichord, organ, or theorbo) improvising harmonies above the bass according to numbers written below it (figured bass).
The figured bass numbers indicate intervals above the bass note, telling the keyboard player which chords to play — but the exact voicing, spacing, and embellishment were left to the performer's skill and taste. This made every continuo realization unique, making Baroque performance a fundamentally collaborative and improvisatory art. The continuo section was so essential that the entire Baroque era is sometimes called the "thoroughbass period." Its decline after 1750 marked the transition to the Classical style.
C.P.E. Bach declared that a good continuo player was more valuable than a good composer — because any competent musician could write a melody, but realizing a figured bass with taste and imagination required true artistry.