MIDI Tesla coil
A video of a musical tesla coil was on the front page of YouTube today. It’s not the only one; there’s a nice one of the Nintendo Mario game theme with a coil for each part (see also: a guitar for each hand).
To get sparks that long, one needs very high voltage electricity. The primary job of the Tesla coil is to step up (transform) the voltage coming out of the wall enough so that it can come out of the dome. It accomplishes this by taking advantage of resonance, usually at relatively high frequencies. The coil in the first video link above resonates at 41 KHz, which is beyond the range of human hearing. So how, then, does this music thing work? In short, the spark itself is being turned on and off so that the plasmafied air is vibrating in the range of human hearing. (The guitar thing works with practice and a good clamp.)
The tunes are controlled via a standard MIDI interface. While large sparks are cool to begin with, and I’m still entranced with MIDI after many years… I wonder if it would be possible to drive the spark with a more complicated audio signal? I remember hearing polyphonic music from Apple ][’s and ///’s, which also had 1-bit (click-based) speaker controllers.