Drop D riff — Dorian colour in B New
A riff built on the B grid (B5d, A5d, G5d): its colour comes partly from the Dorian mode typical of Drop D rock/metal, darker than a major scale but less closed-off than a classic natural minor.
Tips
Isolate by ear the chord that strays furthest from the root before putting it back into the full riff: it's the one carrying the riff's modal colour.
Chord progression — B
Bar 1
B5d
Bar 2
A5d
Bar 3
G5d
Bar 4
A5d