i am surprised that that doesn’t happen more often. With the plethora of record music in our brains, I can see how easy it would be for an artist to think they are composing something original, but in fact is influenced subconsciously by some other recording.
If some skunk really wants to foul the punchbowl, all he needs to do is load a computer up with songs from the top 40s or whatever, and program the darn thing to look for melodic duplicates between them. Then breathlessly clue in the owner of the earlier copyright where duplicates exist.