for those that are curious about how this works, I looked this up when I first saw a couple of these clips cause I was going to make one. Turns out the theory behind it is pretty simple.

The tesla coil shoots out lightning, whatever. the humming of the electricity is ALWAYS at 120hz, the frequency of the juice coming out of the wall its plugged into. The ELECTRICITY is always at 120hz. BUT:

They turn the coil on/off at a high sample rate. This takes the sound coming from the coil to the high amplitude, and low amplitude alternating obviously, faster than 120hz. this means that they can effectively change the frequency of the sound that we hear. If any of you are electrically inclined, its like trying to turn the 120hz into a series of impulse functions to change the frequency domain.