Sampling in Hip-Hop reached its height in the late 80s and early 90s. The legality of using samples from someone else’s song was vague; a lot of djs risked being sued, and ended up doing amazing things by putting together quotations of wildly different familiar music.
Four examples of samples that ended up being used by the band De La Soul:
Makers of pop music have always engineered their songs to sound big and loud. Motown records, for instance, have a legendary, huge sound. Sometimes, though, loudness can be overdone, and this problem seems to be getting worse.
The technology behind this is a device called a compressor. Its job is to keep a volume level consistent. This is great when you want, say, a vocalist to remain audible above the other instruments.