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.
The main melody is made up from an orchestral loop, what i pitched and speeded up, I wrote a voilin melody what I editet and fill up with some reversed piano.
Sample pack @prodbybassyy - WAR LOOP KIT
Loop name Cleaners-140bpm G#m