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 started this song from the main drop lead, after this I made the rest of the drop, the breakdowns and I search for a cool vocal on Splice.
Instrument Vocal Chop
Sample pack SIIK & SIKRATE SOUNDS Vol 2
Loop name SSE2 Vocal Adlip 05 - Amin 128BPM