I remember finding the Beatles stuff hard to analyse.

I IV V songs are the core of rock and pop, II V I progressions the heart of jazz.
Beyond this thre are various other techniques of harmonization.

Many of the Classic works are hard to read and very dry (Piston, Kennon) . The best modern text I have found is called @Harmony for Computer Musicians@ by Michael Hewitt. Don't worry about the term "computer" its a very lucid and non partronising text, there is little that is about computers, but lots about harmony.

Z

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