The Song Fight Bulletin Board

I have an 18 yo family member who can make music noises on lots of different instruments, he played in school bands and can improvise pretty well on sax. He is looking into training in instrument repair. I'd like to convince him that engineering scratches the same itches. basically I'm looking for beginner techie projects for the music minded kid.......
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does anyone have recommendations for beginner kits for building : guitar pedal, theremin, small portable amps, light organ things?

Look Mum No Computer sometimes sells kits/plans for various modular synth modules and usually puts the schematics/bill of materials/etc. on his projects page for free, and there's a bunch of fun little synth project kits you can buy on Amazon and eBay.

The only DIY synth kits I've put together myself are from tastychips.nl and I honestly wouldn't recommend them.

I can recommend a couple of books:

Teardowns: Learn How Electronics Work by Taking Them Apart by Bryan Bergeron

Electronic Projects for Musicians by Craig Anderton

Also, there are a lot of inexpensive and easy guitar pedal kits like: https://buildyourownclone.com/

Or more expensive build or mod your microphone kits: https://microphone-parts.com/