The whole song is the relative-minor world with one secondary dominant — the 3⁷ — locking the door every four bars.
KeyCDbDEbEFF#GAbABbB6/8 · slow arpeggio
Picking pattern (one bar per chord)
e|--------0--------0--|
B|-----1--------1-----|
G|--2--------2--------|
D|--------------------|
A|-0------------------|
E|--------------------| (shown on 6-; keep the shape, move the bass)