See the story of how Paul McCartney and John Lennon's song "Yesterday" was made into a record by George Martin with this clip from Soundbreaking. Martin heard the song's simplicity and decided not to add big, electronic sounds to it, but instead to include a string quartet. McCartney initially opposed the idea, because he thought of classical music as too distanced from who he was as a musician. But Martin convinced him and arranged parts for a quartet. McCartney loved it.
Find more resources in the Soundbreaking collection.