McCartney composed the entire melody in a dream, in his room in the home of his fiancée Jane Asher and her family, on Wimpole Street, London.
Upon awakening, he ran to a piano and played the piece, to keep it from slipping into the recesses of his mind. McCartney’s initial concern was that he had subconsciously plagiarized someone else’s work. So he explained the situation: “For about a month I wandered around asking people in the musical environment if they had ever heard it before. In the end it was like taking a lost item back to the police. I thought that if no one claimed it after a few weeks I could keep it.”
After convinced himself that he hadn’t stolen anyone of his melody, McCartney began to write the lyrics. As Lennon and McCartney used to do, a temporary working text titled Scrambled Eggs was used for the song until something more suitable was found.
It is clear that the first title refers to the fact that the song was written at breakfast time: even if the Beatles have always accustomed us to original and irreverent titles and lyrics, in this case thank goodness that it was then changed in Yesterday, because perhaps it would never have become so eternal and evocative! PR