The same thing would happen to me when I would rap along to lyrics in a song be it by myself or around people, but I didn't know how much it helped until an English teacher in 8th grade had us sing a song in front of the class for an assignment. I picked everything I am by Kanye west. I made sure I remembered all the lyrics the night before and practiced them before I went up. I stuttered on the first three words but once I got the flow going, I rapped the song perfectly. The class went nuts obviously, the silent stuttering kid just rapped a whole ass song without missing a beat. I still get goose bumps thinking about it