http://mto.societymusictheory.org/issues/mto.09.15.5/mto.09.15.5.adams.html
ABSTRACT: This article systematically explores the concept of flow in rap music, with the goal of understanding how rappers’ uses of flow contribute both to the surface rhythmic vitality of a song and to deeper levels of musical meaning. I will explain the three most significant metrical techniques that constitute a rapper’s flow, and give examples of rap songs using each technique. The article concludes with some thoughts on how changes in flow as rap music evolved contributed not only to different style features, but also to value judgments by both rappers and audiences.
Feel free to check this out, a good article by Kyle Adams at Indiana University on the very exciting rhythmic complexities of rap music. Not only that, but how it evolved from the styles of the mid-late 80s.
