Bass notes in guitar?

I think of it similar to Aerials by System of a down, It uses drop d with the lowest 3 strings and tends to use the same position.
—-2-3-2-0
-0
3
The main change involves changing the note on the low D which changes to an open and then a variation played with a 5 fretted on the low D and open A and D
—-0———-5-2
-0-0—————
5——-0————
To get the effect Syn is getting it involves arpeggiating from low D to d but instead of returning to Low D by playing the strings in between you skip them.
In essence you play this
Low D- A string- D – Low D and the cycle repeats
Watch this if you are still unsure of the technique

Yeah, he’s right, the bass note just ascends the D minor scale. D-E-F-G. Here’s a quick video of it slow and up to speed. I also, played the next main part and then part of “Nightmare” just to show they are the same progression and how you can play more or less the same thing and get a totally different vibe.