It all started with sampling. Rappers would sample beats/melodies from other songs to rap over and make their own. Vanilla Ice “Ice Ice Baby” is a sample of “under pressure” by Queen and David Bowie; “Ice Ice Baby” was a real hit too. Artist still do it too this day, e.g. Jason Derulo. But not just famous artists, anyone could do it. Here is an amateur video of some kid rapping over Drake’s “Forever”.
Sampling then evolved into remixing, meaning old songs could be relived and given an modern sound. Example of this include, Kygo’s remix of “I See Fire” by Ed Sheeran, and Tracy Chapman’s “Fast Car” by Jonas Blue ft Dakota. Remixing has been revolutionary for the music industry allowing room for new artists to add new ideas to old music. It is a fantastic experience for both the artist and the listener.