June 14, 1965…At EMI's Abbey Road Studios in London, the Beatles recorded "I'm Down," which became the B-side of their single "Help!" During the session, Paul McCartney kept repeating "plastic soul, man," a reference to Mick Jagger's version of  rhythm & blues. The expression later evolved into the title of their next album, "Rubber Soul."

After the group completed "I'm Down," Paul McCartney recorded two takes of his song "Yesterday." Three days later, a string quartet was overdubbed on take 2 and that is the version that was released, with none of the other band members included in the final recording.