What does the term 'continuo' refer to in music?

The term 'continuo' refers specifically to a bass part that includes numbers indicating chords to be played, which provides a harmonic foundation for the music. This technique is prevalent in Baroque music, where the continuo is typically realized by keyboard instruments or continuo instruments, such as the lute, along with a bass line. The numerical indications, known as figured bass, guide the performer in realizing harmonies that enrich the musical texture.

In contrast, other options present different concepts in music. A melody part written out in full typically refers to a clearly notated melody line, which does not encapsulate the idea of continuo. A harmonic structure without written bass suggests a scenario where chords exist but lack a grounding bass line, which does not align with the definition of continuo. Lastly, a vocal line supported by orchestral instruments describes a different relationship, where the focus is on the vocals, rather than the accompaniment structure that continuo provides.