From Good Math, Bad Math.

Ladies and gentlemen.. For your pleasure and edification, allow me to present… The singing Tesla coils!

Yes, if you’re clever, and you’re willing to do a whole lot of work, you can operate a Tesla coil so that the sparking from the coil produces a particular pitch. Even you’re even more clever, you can vary the way that the coil is run to produce different pitches, and arrange it into a song. And if you’re really remarkably clever, you can set up two singing Tesla coils, and have them play a duet.