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Puzzle boxes: locked boxes that unlatch by playing an electronic game, like Simon:
or Tetris:
Speakers for home audio, both passive and powered.
Portable speakers, bluetooth speakers and boomboxes.
Guitar practice amps/speakers, combo amps, busking amps, with built-in effects.
Electric guitar fabbing and modding.
Modular synthesizer racks.
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Toy pianos and
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synthesizer keyboards:
This one has keys made out of laser-cut birch ply, but I'm working on a version with bamboo keys – they're more flexible and look better.