Pusha T on Unpredictable Lyrics

Interesting RapGenius annotation from Pusha T himself on his fantastic new song, Crutches, Crosses, Caskets:

[Puff] told me that if he could see where my next line was going then that’s the wrong line. 

I can remember being in the car listening to Big verses and asking “What in the world makes Big think he can rap about a shootout, the love of his daughter, balling at All-Star in six bars?" 

How do you transition that? 

Puff telling me he doesn’t want to see where I’m going in a verse is the best explanation I got to answer questions pertaining to my favorite artist.

Is unpredictability truly the secret to great lyricism? Certainly it's one aspect of it, but can it be overdone, coming at the cost of coherence and narrative?