True rappers practice their skill on the mic and is able to create on the spot because they have applied themselves to the practice and experiences that are necessary to be a freestyle MC. There is no abnormality about it. It is the simple fact of practice, practice and more practice. I experience the same phenomenon when I am telling a story or speaking publicly. Everyone that has worked on a skill in life has experienced this. I have done it so long it is as simple as drinking water. checkout the article
Peace & 1hunidyears
Rappers' Brains: Relaxed 'Executive Function' May Enable Freestyle Raps:
'via Blog this'