As mentioned in Lesson 9, call and response is a typical Blues and Gospel technique where one instrument or voice answers another. In the following example, the harmonica does not play in the first two bars. The vocalist sings in the first two bars and the harmonica answers in the following two bars. This format is then repeated for the rest of the 12 bar progression. Many Blues songs are played in this exact manner. Try singing a line and then answering your voice with the harmonica, or get a friend to sing and you answer with the harmonica.