[pessimizer]

There's no 30 second rule for sampling - IIRC the limit to sampling is how many people you want to negotiate a composition credit with. That's why newer music that uses popular samples usually just sounds like an annoying remake of a song that was good enough already. This creates an image in the public mind that people who sample aren't very creative at all, just turning up the bass and shouting over old songs.

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>