If you have a recital to do, you have to memorize the songs. I never use music when I do recitals. It produces an instant barrier, both for yourself and the audience. ↗
Jay-Z is like a rap-savant, he doesn't have to write the rhymes down, he can create complex raps in his head. I mean he does memorize it, he just doesn't write it down on paper. He doesn't freestyle onto the track, it's all thought out. ↗