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.
In this project I used mainly Serum, everything is well-organised.
Sample pack Odyssey - Zenhiser
Loop name 023_a__Synth_Loop_1__With_FX_Trail__122bpm_D