Think I'll agree on Script, to me it does sound like a since wave subbass. IF that is what you're pointing out, when I pull it in FL and look at the oscilloscope, looks like this(Lowpassed everything else but that.)  http://prntscr.com/bks8du . Although, it's not stable like if you just hold it and have nothing on it. It does wobble, and not by when the note changes but it looks like it bounces up&down just a very tiny bit. Sounds like something I do since I just don't want a regular sub on the bottom. I'm new too and struggling with basic sounds as well, but that's my take on this xD Hope this helped somehow.