Music: a singing style that features a leader who is imitated by a group is called:

The correct answer is "call-and-response"

Explanation:

This is a music style in which the melody is set in a phrase that then a following one comes up to ample the idea. It is something similar as a conversation, the first phrase of music is used as the call and the answer is another different phrase of music. This phrases can be vocal, instrumental or even both.