Wonder how Rap music fits in to this theory?
Not sure, but definitely something to think about. Wordplay comes into it as well as rhythm of delivery and meaning/non-meaning of the words.
REM’s It’s the End of the World As We Know It (And I Feel Fine), itself in the tradition of Subterranean Homesick Blues, is a good example of what I mean:
Light a candle, light a votive
Step down, step down
Watch your heel crush, crushed, uh-oh,
This means no fear cavalier
Renegade steer clear!
A tournament, tournament, a tournament of lies
Offer me solutions, offer me alternatives and I decline
Like... What does all that even mean? So it’s just like Michael Stipe is playing his own voice as opposed to delivering a narrative through verse.