Reading your comment I remembered a story I heard about Jimmy Reed. Who knows if it's true, but the story was that he wasn't sharp enough to remember the words to his own songs, and his wife had to stand behind him on stage and whisper to him to remind him. Hell of a blues player though
https://www.youtube.com/watch?v=l9xXchxodYg https://en.wikipedia.org/wiki/Jimmy_Reed