What is the style of singing without prior preparation or practice in leader-chorus form.?

The style of singing without prior preparation or practice in leader-chorus form is known as call and response. It involves a soloist (the leader) singing out phrases, which are then repeated by a group (the chorus). This musical technique is commonly found in African-American spirituals, Gospel music, traditional African music, and even in modern-day pop and folk songs. Call-and-response singing not only creates an interactive experience between the leader and the group but also strengthens the sense of community and adds an evocative storytelling aspect to the music.