Well, I listened to it all the way through. Not my jam, but...

Online sources suggest the chords are Bm, Em and G. The notes B, A and D "fit" over those chords while creating a repeating kaleidoscope of tension and release.

To your question of "How do you usually find these repeated notes?"...

I find motifs by listening to the harmonic movement and overlaying my musical ideas. Sometimes the motif will not change, sometimes a note or two will change to provide a musical twist that I like.

The idea of a repeating melodic line has a lot of contexts, not all of them modern. Springsteen's "Born in the USA" is basically one melodic line played over two chords. Worked for him.

Good luck!

DC Ron
BiaB Audiophile
Presonus Studio One
StudioCat DAW dual screen
Presonus Faderport 16
Too many guitars (is that a thing?)