On many albums, The Beatles presented a highly polished sound. A great example is “Yesterday,” the track from Help! that became the band’s most popular song of all time. With a string section behind him, Paul McCartney’s classic tune sounds perfect from a production standpoint.
While they’d drop all formalities for rocking tracks like “I’ve Got a Feeling” and “I Dig a Pony,” The Beatles would always mix in heavily produced songs, sometimes with guest musicians. That was only possible with someone able to read and write music for string players hired for the job.
However, The Beatles weren’t handling that part of the recording process. They might be able to sing or suggest what they wanted, but it was up to producer George Martin to put it on the page. (The medley on Abbey Road is a good example of Martin’s handiwork.)