The Dorian mode is spelled: 1 2 ♭3 4 5 6 ♭7; or, in steps: whole, half, whole, whole, whole, half, whole. It’s frequently employed by jazz, soul, and rock soloists, and can be found in the “jam sections” of tons of classic rock and jazz tunes from players like Carlos Santana and David Gilmour (as well as jazz improvisers like Miles Davis).
The bass blends well in this mix and grooves solidly throughout the whole song. But one recurring motif that sticks out, perhaps because of the space created by the choppy, Kinks-esque guitar riff, is the simple walk-up to the fifth (an E over the A chord) via the major third and perfect fourth. It happens after the first four chords (which, on their own, actually sound like a rewrite of “You Really Got Me”), and tucks nicely into place as the short D and A guitar chords follow it and carry the end of the measure into the G and C chords of bars 3 and 4. The pattern is repeated over these bars, and basically everywhere else in the song involving the main guitar riff, though East varies it almost every single time with masterful subtlety.