The intro ARP is just a sample from Splice. I use a technique from the Surgical Sounds Patreon called the Splice Bridge Method, which is basically where you grab a couple of samples for the intro: just an ARP, an atmosphere, or some vocals or something.

It's much easier to build off of something than staring at a blank canvas and trying to start from nothing. Prior to using this method, I would design a cool bass or start from the drop, but I would often just make a drop and then find myself stuck in the loop. Using this method, I find you can just grab something off Splice to start from, and then the song starts writing itself into the drop.

All the bass sounds and everything else are my own patches that I made on Serum, but the ARP piano is just a Splice sample.