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 did a fat bassline using NI Massive, doind the low-mid part of the song. For the sub, I used Serum and I add a special trick that gives to it a good harmonic aspect. I also used the newest/fresh samples, individually well processed so it can fits perfect on the track.
Instrument Bass Shit2 (Robotic Ambiance)
Sample pack Disciple Samples - Virtual Riot x Modestep Spicy Riddim Drums Vol. 1
Loop name V_RIOT_MDSTP_bass_shot_savannah_02_C#