One morning in the 1960s, Paul McCartney woke up with a beautiful melody running through his head. It was so complete, and so familiar-sounding, that he was convinced somebody else must have written it.

He had just dreamed the tune that would become "Yesterday," one of the most celebrated songs in popular music.

McCartney was staying at the London home of his girlfriend, actress Jane Asher, and her family. His small bedroom had a piano beside the bed. When he awoke with the melody in his head, he went straight to the keyboard and worked out the chords before the music could disappear.

But something bothered him. The tune sounded like an old standard, perhaps a song by Cole Porter or something his jazz-loving father might have played. McCartney couldn't believe he had composed it himself.

For weeks, he played the melody for anyone who might recognize it. He asked John Lennon, George Harrison, Ringo Starr, Beatles producer George Martin and other musicians whether they had heard it before.

Nobody had.

Gradually, McCartney accepted that the melody was his. Now he needed some words.

To preserve the rhythm while he worked on the lyrics, he gave the song a temporary title: "Scrambled Eggs." Its opening words were hardly destined for immortality:

"Scrambled eggs, oh my baby, how I love your legs."

The melody stayed with him for months before the proper lyrics took shape. During a trip through Portugal with Asher in 1965, he worked out much of what would become the melancholy love song we know today.

When the Beatles recorded "Yesterday" that June, McCartney sang and played acoustic guitar accompanied by a string quartet. It was the first Beatles recording released under the group's name to feature just one member performing.

The song reached No. 1 in the United States and went on to become among the most frequently covered compositions in popular music.