George Harrison was found guilty of subconsciously plagiarizing the 1962 tune "He's So Fine" by the Chiffons in his song "My Sweet Lord" (1970).
In his speculative story Melancholy Elephants (Penguin Books, 1984), Spider Robinson writes about the pros and cons of rigorous copyright. The setting is half a century from now. Population has increased dramatically, with many people living past 120. There are many composers. The story centers on one person's opposition to a bill which would extend copyrights to perpetuity. In Robinson's future, composition is already difficult, as most works are being deemed derivative by the copyright office. The Harrison case is cited as an important precedent. Then, in the late 1980's, the great Plagiarism Plague really gets started in the courts, and from then on it's open season on popular composers. But it really hits the fan at the turn of the century, when Brindle's Ringsong is shown to be "substantially similar" to one of Corelli's concertos.
Robinson points out that the currently prevalent system of composition has a limited number of specifiable notes which can be combined in a large but finite number of ways:
Artists have been deluding themselves for centuries with the notion that they create. In fact they do nothing of the sort. They discover. Inherent in the nature of reality are a number of combinations of musical tones that will be perceived as pleasing by a human central nervous system. For millennia we have been discovering them, implicit in the universe--and telling ourselves that we "create" them. To create implies infinite possibility. As a species, I think we will react poorly to having our noses rubbed in the fact that we are discoverers and not creators. (P. 16.)