What musical form is characterized by a musical line responding to a previous line?

The musical form characterized by a musical line responding to a previous line is call and response. This form typically involves a "call," which is a phrase or section presented by one musical voice, followed by a "response," which is a phrase or section that complements or answers the call. This interaction creates a conversational and dynamic musical texture, often found in many styles, including folk, gospel, and jazz.

In contrast, theme and variations focus on altering a primary theme through different interpretations rather than a direct exchange between parts. Binary form consists of two contrasting sections (A and B) but does not inherently involve a responsive relationship. Sonata form includes exposition, development, and recapitulation sections, which are more complex and structured rather than simply involving a call and response dynamic. Each of these forms serves unique structural purposes in music, but call and response specifically highlights that interactive quality of musical dialogue.