While Ed Sheeran just won (in my opinion, thankfully) his copyright lawsuit, the writers of "Blurred Lines" famously lost the lawsuit filed by Marvin Gaye's family alleging infringement of "Got to Give it Up". In my opinion, that was the wrong decision - while you can argue there are some similar beats and chord progressions, I don't see how anyone could believe that Blurred Lines isn't at least a "transformative" depiction of "Got to Give it Up" (to be clear, I think it's much more than that - the songs sound completely different to my untrained ear). Even in cases where there is no dispute, where one song legally samples another song but pays royalties, in many cases the use of the sample is completely transformative, again in my opinion, use of the original song.
So basically what I'm asking is why do judges appear to apply the "transformative" rule to visual arts but not to auditory ones.