What is the fine-grained topic of the following text: Reggae, as many genres, has gone through its ups and downs in popularity and has been affected by other styles of music from rap to techno, but the classic roots reggae with its Rastafari connotation most identified with Bob Marley, has always been the standard by which genuine artists of the genre are measured. Only return the topic.
The impact of various music styles on the evolution and assessment of Reggae music.