Sentence:  They make much ado over Bob Dylan as a <WSD>proto-rap</WSD> pioneer, and taunt Public Enemy for being "unable to locate even one pure black source" (begging Chuck D's own question in "Fear of a Black Planet": "Who is Pure? What is pure?"). 
Meaning of the word marked with <WSD> tags:  Performance art forms that served as precursors to rap, especially those that feature rhythmic spoken and/or half-sung lyrics.