Wikipedia
Lennon–McCartney (or McCartney–Lennon) was the songwriting partnership between English musicians John Lennon (9 October 19408 December 1980) and Paul McCartney (born 18 June 1942) of the Beatles. It is one of the best known and most successful musical collaborations in history, with the Beatles selling over 170 million albums, more than any other band. Between 1962 and 1969, the partnership published approximately 180 jointly credited songs, of which the vast majority were recorded by the Beatles, forming the bulk of their catalogue.
Unlike many songwriting partnerships that comprise separate lyricist and composer, both Lennon and McCartney wrote words and music. Sometimes, especially early on, they would collaborate extensively when writing songs, working "eyeball to eyeball" as Lennon put it. Later, it became more common for one of the two credited authors to write all or most of a song with limited input from the other.
By an agreement made before the Beatles became famous, Lennon and McCartney were credited equally with songs that either one of them wrote while their partnership lasted. Lennon–McCartney compositions have been the subject of numerous cover versions. According to Guinness World Records, " Yesterday" has been recorded by more artists than any other song. The Sunday Times called Lennon and McCartney the greatest composers since Ludwig van Beethoven.