The basso continuo was usually made up of two parts, a bass part played on a keyboard instrument, typically the harpsichord, and a figured bass line, often written on a separate sheet of music, indicating which chords should be played. The chord quality (major, minor, diminished, augmented) and any accidentals were typically indicated by figures and symbols placed above or below the bass notes.
The basso continuo had several functions in Baroque music. It provided harmonic support to the melody, outlined the chord changes, and helped to establish the tempo. The continuo player was also responsible for following the harmonic intentions of the composer and responding to the changes in the music at the moment.
The basso continuo was used in many different types of Baroque music, including operas, cantatas, sonatas, concertos, and chamber music. Some famous composers who wrote for the basso continuo include Johann Sebastian Bach, George Frideric Handel, Antonio Vivaldi, and Arcangelo Corelli.