The Beatles is a major indicator, for this purpose, 1963 onwards.
They were the greatest thing happening for music, at the time. Artists and producers tried to succeed, according to new standards set by the Beatles.
At this date – February 14 – i do not have a full data material on the Beatles. However I have some material.
One analysis of the way “love” is treated in Beatles songs, suggesting three main periods:
1 Mixed – communal. E g She loves you, which not only tells of a woman active, loving a man, but another man, lovingly giving the message. A mega hit of all time, due to this special angle.
2 More troubled – from I feel fine, to Ticket to ride – also gradually, more private, less communal or collective. Increasing misogynism.
3 More reflective – from All the lonely people, She’s leaving home, and onwards. Less directly realist, more widely experiental. Reduction of misogynism.
Later we heard J0hn the main Beatle like he was divorced, Paul happy with Wings, and so on. But I think these were the three main Beatle stages.