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.
Sample downloaded from the looperman site, free to use .. 808 from spinz and beat with southside s
tyle 808 mafia
Sample pack Looperman
Loop name Guitarra Banger para Pyrex Whippa Gunna Dababy