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This may sound weird, but...

I am attempting to design a steampunk / gothic horror-styled electric harpsichord, with sparkgaps as the sound source in the vein of musical Tesla coils.

Unlike musical Tesla coils, any particular spark generator need not be dynamically tunable for different frequencies--there will be 88 of them, one per keyboard key, manually tuned to a single note at a time. I would prefer if the frequency could be tuned by screwing a threaded steel rod into or out of a solenoid to alter inductance, but a potentiometer or variable capacitor any other sort of mechanically-adjustable tuning component is acceptable. Also unlike musical Tesla coils, the sparks need not terminate in open air--and I imagine it's probably best if they don't, since there will be 88 of these things packed fairly close together.

To fit the aesthetic, it would be ideal if such a circuit could be constructed entirely out of resistors, capacitors, and inductors--i.e., discrete components that I can make by hand by winding wire into coils, rolling up laminated sheets of metal foil and paper, etc., but if a transistor or or diode or something is required per spark generator, so be it.

The intended behavior is that, on activating a switch (keyboard key), a spark should be generated which produces a specific audible tone, and either continues indefinitely while the switch is activated, or decays after a fixed but significant amount of time (analogous to a plucked string ringing down).

What is the simplest / most robust circuit I could build to do that?

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    \$\begingroup\$ It'll probably be much easier to build a "musical Tesla coil" and have your keys activate tones that you feed to the Tesla coil. Tesla coils are usually resonant at frequencies way above audible. Musical Tesla coils modulate the high frequency drive with the audio signal. \$\endgroup\$ – JRE Jul 11 at 20:36
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    \$\begingroup\$ I'd recommend building it out of "regular" components first. Get it working, then convert to your hand built parts. Here is a link on how a spark gap transmitter works from the ARRL: arrl.org/files/file/History/… They even talk about the sizzle of the arc vs getting a tone. \$\endgroup\$ – Aaron Jul 11 at 20:44
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    \$\begingroup\$ Resonance at audio frequencies will be challenging ... \$\endgroup\$ – MadHatter Jul 11 at 23:36
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I am attempting to design a steampunk / gothic horror-styled electric harpsichord, with sparkgaps as the sound source in the vein of musical Tesla coils.

The device you are describing is, functionally, very similar to a spark-gap radio transmitter. The use of these devices has been banned by international law (!) since the 1930s, as they produce wide-band radio interference.

Unless you have a specific, detailed plan in mind for preventing this device from producing radio interference and confirming that its emissions are negligible, I would recommend that you consider alternative effects, or a simulation of a spark gap. The potential for a device like this to cause havoc by (e.g.) interfering with public safety radio systems is too great.

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    \$\begingroup\$ There doesn't seem to be any problem with musical Tesla coils; I presume that is because they use high frequency AC sparks, and get the tone by turning the spark on and off, rather than resonating at audio frequencies directly. But in case the device does produce notable radio interference, I had intended to shield the row of spark generators with a wire-mesh Faraday cage. \$\endgroup\$ – Logan R. Kearsley Jul 11 at 21:34
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    \$\begingroup\$ Any spark generator creates tons of RF harmonics, even Tesla coils. I'm thinking Tesla coils fall into the "It runs for a few minutes, looks cool, then it sits in the garage for 15 years before being thrown out" category, so isn't much of a concern. I'd say definitely use a Faraday cage. That shouldn't affect the sound noticeably. \$\endgroup\$ – rdtsc Jul 11 at 21:56
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    \$\begingroup\$ On further consideration, devices like tasers and Jacob's ladders are also not banned. So, yeah, I'll use a Faraday cage to be safe, but as long as I don't attach an antenna to it, the magnitude of RF noise should be manageable. \$\endgroup\$ – Logan R. Kearsley Jul 11 at 22:03

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