The leader sings or plays a phrase and the audience sings it back. This musical form is called ________.

The musical form you are describing is called "call and response." In this interactive form of music, one party (the leader) presents a musical phrase or vocal line, and the other party (the audience) replies with a corresponding phrase. This structure is commonly found in various musical genres, including gospel, blues, jazz, and traditional African music.

The call and response format not only enhances the participatory aspect of music but also fosters a sense of community and engagement among performers and listeners. It allows for improvisation and personal expression while maintaining a cohesive musical framework, making it a fundamental element in many cultural musical traditions.