When I'm Sixty-Four
When I'm Sixty-Four is a Beatles song, written by Paul McCartney (credited to Lennon/McCartney) and released in 1967 on the album Sgt. Pepper's Lonely Hearts Club Band.
The song, which features a clarinet trio, is sung by a young man to his lover, and is about his plans of growing old together with her.
The song is in the key of D-flat major. The Beatles recorded the song in C major, but they sped up the master in order to raise the key by one semitone at the insistence of McCartney, perhaps to make his voice sound younger.
Tutorials
Sheetmusic
Use a Google Image search. Matching the first measure should find you the score.