During the golden age of rap (aka the only reason rap entered worldwide mass consciousness), the music would be stitched together from half a dozen or more manipulated and overlaid samples of songs, often of sub-second length. After a few high profile lawsuits, rap was neutered into the type of party pop where it would be considered notable that samples were less than 30 seconds.
Listening to, for example, a Bomb Squad produced song from the era, you could have previously been familiar with every single song that went into the production, yet be hard put to spot more than one or two.
I'd liken the situation to trying to write a program in a world where there's a billion libraries that you can use, but for each one you have to share 25% to 75% of the profit from the program with the owner of the library. In addition, these billion libraries would be criss-crossed with a million patents, assuring that you can't simply reimplement the functionality without running into the same problem.
</why I stopped listening to rap in 1995>
If anything a low literacy rate probably means that people are less exposed to the concept of "droit d'auteur", a concept internationally established at the Berne Convention by the literary elite in France (victor hugo, et al).
The concept of copyright is largely grounded in written works. If anything the recorded music industry was one of the first to challenge "right of the author". The sheet music industry was up in arms when recorded music became mainstream.
I also get the impression that writers are generally more likely to be adamant about copyright that musicians. When you are producing 4 minute songs versus 200 page tomes, there is a much greater chance that whatever work you are producing will demonstrate elements of the works that influenced the author.