Items from the shanty and sea song repertoire have been brought into the repertoires of performers of folk music, rock, and Western classical music. Sources for these renditions include books by folklorists and commercial recordings by shanty revival performers. The forms these performers produce tend to be quite standardized and relate to their source material similar to the way a cover song does. This can be contrasted with the method of performers focusing on maritime music, who tend to think of themselves as operating within that genre or a tradition, and who develop their repertoire from multiple sources and through various experiences.