Ladies and gentlemen, may I present to you the newest (and oldest) thing in electronic musical instruments, the tesla coil:
(I got this from ocschwar, though not via LJ. His info pointed me to a page that wouldn't play the video in my browser, but included the following info:
Steve Ward's Singing Tesla CoilThat page also mentions some proposed names; the one I like is the title of this post.
This is a solid-state Tesla coil. The primary runs at its resonant frequency in the 41 KHz range, and is modulated from the control unit in order to generate the tones you hear.
So just to explain a little further, yes, it is the actual high voltage sparks that are making the noise. Every cycle of the music is a burst of sparks at 41 KHz, triggered by digital circuitry at the end of a "long" piece of fiber optics.
What's not immediately obvious in this video is how loud this is. Many people were covering their ears, dogs were barking. In the sections where the crowd is cheering and the coils is starting and stopping, you can hear the the crowd is drowned out by the coil when it's firing.
This Tesla coil was built and is owned by Steve Ward. Steve is a EE student at U of I Urbana-Champaign.