When I'm Sixty-Four was written by Paul as a kind of tribute to his father, who was a band leader in the 1920s. This simple musical style was starting to make a comeback at this point in time; 1967. Paul has said that he was about 15 when he wrote the song, which would be 1957 or 1958. Coincidentially, his father Jim was 64 when the song was released. The song is about a young man trying to persuade a young lady to marry him and stay with him forever, then asking her to get back with him when she decides, suggesting a casual, haphazard proposal. "The words are slightly mocking," George Martin commented.
In order to make Paul sound younger, the recording was sped up one semitone for the final master. Two clarinets and a bass clarinet were played by Robert Burns, Henry MacKenzie, Frank Reidy.
"Paul completely. I would never even dream of writing a song like that. There are some areas I never think about and that is one of them." - John Lennon, Playboy, 1980