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.
Original track..Used and modified guitar loop.
Sample pack Cymatics - Destiny Mystery Expansion
Loop name Cymatics - Days Gone By - 100 BPM D# Min