in fl studio i use edison's detect pitch regions tool to see the different note's to come to a key..
as for the fluid of chopped samples together i'll have to side with pure feeling cause the great beatmakers don't have a secret just a great ear and shitload of work hours.
i would like some of you to hear two cat's from my home country of Croatia...
this is his channel,he works with a whole new wave of rappers who brought the scene some much needed life and after a brief trip to trap he started to produce songs which sound like dj premier had a kid with j dilla
i know some of you will think my post is out of place but trust me those cats have mad sampling technics and if you can bare to listen to ppl rapping in an unknown language you'll hear pure hart of sampling in hip hop