Love was such an easy game to play
Paul McCartney wrote the music for yesterday while dreaming at his girlfriend's house, English actress Jane Asher.
When Paul woke up he quickly played the tune on the piano so he wouldn't forget it. McCartney was so paranoid that he plagiarized someone else's tune that he spent a month playing it to various musicians, asking them if they ever heard it before.
After realising his music wasn't plagiarism, he started to add the lyrics.