This musical directive indicates that one or more instrumental parts should closely follow or double a vocal line. The instrumental part is thus subordinate to the vocal melody, primarily reinforcing and supporting it rather than introducing independent melodic material. An instance might involve a string section mirroring the soprano voice during a lyrical passage in an opera.
Employing this technique enhances the clarity and projection of the vocal melody, particularly in situations where the vocal part might be easily obscured by a dense orchestral texture. Historically, it served as a practical means to ensure vocal prominence in compositions pre-dating modern amplification technology. It also offers composers a method to subtly color and enrich the sonic palette surrounding the voice without overshadowing it.
