At 1:15 Nigel pushes/clicks/opens something and the tones go deeper. Is that the Hurdy Gurdy, or what is making that deep sound? I won't lie, I am absolute mesmerized with the HG!
He flicks several more strings on, which had not been touched / made to sound by the wheel. And the last string is the big bass drone, which he tunes till start of the solo at about 01:53