if lawyers are going to keep foisting themselves onto art at the behest of studio/record execs, then at least do it by degree and not make it a yes/no binary
it's 57% similar, therefore there should be 57% recompense
I think that's actually a pretty impractical idea - and would result in a massive proliferation of music copyright suits. Anytime someone has a big hit and someone else can win a "10% similarity" and get 10% of the revenues? Goodness, no.
The standard is "substantially similar" and often involves an almost forensic analysis of the music - but unless there is a clear "theft" of the music, such as the case of a direct sample, the question of substantial similarity can be a bit vague, and based on whether a typical listener would think it was substantially borrowed from the previous work.
But it is contrasted with "not substantially similar" that even allows for de minimus similarity, which seems reasonable given that in western music, especially western pop music, the range of tones and sounds that are typically employed is somewhat narrow.
So there's a threshold of what qualifies as "substantially similar" - and anything that isn't found to be substantially similar isn't a violation and owes nothing.