What does the Italian musical term "colla voce" instruct musicians to do?

The term "colla voce" is an instruction for instrumentalists in a score to follow the singer's lead. This means that the instrumental parts should be played in a way that supports the vocal line, adjusting dynamics, tempo, and phrasing to match the singer's interpretation. This instruction is particularly common in concertos and operatic music, where the relationship between the singer and the accompanying instruments is crucial for achieving a cohesive musical performance. The essence of "colla voce" lies in collaborating closely with the vocalist, allowing for a more fluid and expressive rendition. This is why the choice that indicates following the singer is the correct answer.