This is a continuation of the description this inventor attached to the video:

The music your hear is only from the arc and nothing else. There are no other sources of music in the room. It works by using a 555 timer to convert an audio input signal into a frequency modulated signal used to drive a flyback transformer.

And here is a description of the state of plasma as cited from wikipedia:

Plasma (from Greek πλάσμα, “anything formed”^[1]) is one of the four fundamental states of matter, the others being solid, liquid, and gas. A plasma has properties unlike those of the other states.

What do you think does this sound bizarre or what!  Feel free to comment with your ideas and keep a lookout for more cool devices from this inventor.