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 hooked up a sample shot, then did the bassline, drum sessions and added a vocal from the Splice.
Sample pack Sample Magic - Night Funk & Nu-Disco
Loop name nfnd_122_keys_loop_lux_Bbmaj