Help for the meaning of a sentence

[Bushwhacker]

I don't quite understand the following sentence:

"Lennon had come to associate the elaborate musical arrangements of much of the Beatles' later work with Paul Mc Cartney and George Martin."

Does it mean that "Lennon, alongside with Paul Mc Cartney and George Martin, got to elaborate musical arrangements of much of the Beatles' later work?

Or maybe that "Lennon did the elaborate musical arrangements of much of the Beatles' later work but let the work was also attributed to Paul Mc Cartney and George Martin? That's to say that officially the three are responsibles for the arrangements and not only him, besides the fact that there were made by him, mainly.

What a mess. Any help'd be much appreciated.

Bushwhacker

[Anglika]

Lennon regarded the elaborate musical structures of later Beatles' work as being the work of McCartney and George Martin, in which he had little input.