Kathakali Music is the voice of Kathakali. It is the singer who describes the scenes and present the dialogues for the characters. If you have watched a Kathakali performance, you must have noticed the role of music and rhythm in Kathakali, especially the involvement of the singer.
Kathakali music belongs to the Sopana category of music. It is more rhythm oriented so as to enhance the acting on the stage.
Compared to Carnatic Music, Kathakali Music is more about improvisation than following a structure.