That song takes me through so many emotional stages of the plotting. All the way from "this is nice" via "I can make it nicer" and "I have just the idea", eventually devolving into the cackling phase of assembling a cohort of minions to do my bidding. The song ends when I have a finised and fully assembled evil contraption on the desk in front of me.
Tip: High fidelity and Loud!
Alternatively, while building my doomsday devices, the Kerbal Space Program VAB music works well.