I would draw the line at "Sgt. Pepper." Anything before that could be considered early, and anything after that could be considered later.
Yes, I know some of those "early" albums were also very experimental, i.e. "Rubber Soul" and "Revolver," but they were still pop albums for the most part, albeit ones with more adventurous sounds and lyrics.
BTW, I'm just generalizing. I know some of you are going to split hairs over this and disagree vehemently, and that's fine. This is just my viewpoint.
Sander Smeenk said:
I think I'll go for the early beatles. Just simple rock n roll songs instead of strange sitar plucking. But that doesn't mean that every later beatles song. Some are even better than the early ones in my opinion (Julia, Taxman, Magical Mystery Tour). And also, when is something early and when is something later?