I was looking up the proper term for a plasma lamp and stumbled upon the Wikipedia entry for the Zeusaphone.
It’s a Tesla Coil that’s set up to modulate its discharges so that they produce specific notes. In other words, it’s a Tesla Coil that plays music using lightning!
Seriously… how can you turn down a description like that?
It’s also been called a “thoremin,” — another lightning-god-based pun, this one on the theramin,
The company that makes them has a couple of video clips on their website, but sadly they’re a little underwhelming on a 200-pixel window with computer speakers. I imagine they’d be seriously impressive in person.