What does The Author means By "string-along songs about razor blades" (champion of the world - Maya Angelou)

By saying "string-along songs about razor blades", the author is referring to the fact that "radio-prize broadcasts" was sponsored by Gillette

Explanation:

Champion of the World is a chapter in the book I Know Why the Caged Bird Sings by Maya Angelou. The chapter describes a situation in which everyone is gathered in the store owned by the author's grandmother and her Uncle Willie to listen to a boxing match. In that event the author mentions the radio broadcast about razor blades.

"String-along songs about razor blade" were the author's narration of an advertisement on razor blades.