Just saw a BBC analysis of the problem with using chord progression (including the equation of chord extensions with ordinary chords) as as a copyrightable unit. Of course Sheeran is right; the Marvin Gaye estate is simply trying to capitalize on their previous success. (I'm not a Sheeran fan--but he's clearly justified in his stance, and he is defending all creative musicians in doing so.)

The Andy Warhol suit is going to come up some time soon in the Supreme Court. It'll be interesting to see what the current divided and divisive batch of justices decide and (more importantly) how they justify their ruling(s). It's about visual art, but there could be repercussions for written and musical texts as well.