Socalled and Sampling.

In music, sampling [wiki] is the act of taking a portion, or sample, of one sound recording and reusing it as an instrument or element of a new recording. This is typically done with a sampler, which can be a piece of hardware or a computer program on a digital computer. Sampling is also possible with tape loops or with vinyl records on a phonograph.

In this neat clip, Socalled explains his philosophy behind finding and using a good sample of existing music, he says "it's like they put it there 80 years ago so that we could use it now."

Click play or go to Link [YouTube].