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 idea with the drums and then the vocals, and I added the rest of the elements, this song has a somewhat sad and melancholy character
Sample pack SIIK Sounds - SLCTD Collections
Loop name SLCTD Atmosphere 19 Amin 126BPM