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.
I used a great guitar sample what I flipped and edited, than I completed with other instruments.
Sample pack BUYLOOPS.COM - Free Loops Vol. 38
Loop name Loops\Hold Up 120 C#min (Prod. SouthGangBEATZ).wav