The base is original from the producer (chords and melodies), but is complemented with elements that complement the song that come from samplepacks, usually, vocal chops, guitars, wobbles sections, glitch effects. It is the standard in which most of producers work, in a project you will find MIDI files made by the producer, but also melodic loops.
Melody used one time as loop and another chopped and edited
Sample pack Cymatics VYPR
Loop name Cymatics - VYPR Various Melody Loop 2 - 88 BPM A Min