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.
Bassline has two layers, the main bass and melodic top bass, both made using Serum. The other synth used in this project is the arp, which is made with a modified and processed FLEX preset. In the second part, an edited royalty-free synth loop is added in the background to create a little fuller sounding drop. The track is completed with some FX, atmospheres and ambience loops/samples.
Sample pack mau5trap: Random Label Pack
Loop name BGUMMY_arpeggio_loop_unseen_128_C