InMusic/Akai/Alesis/Numark are hiring. Just learn C/C++ and JUCE and read a few digital signal processing book, you're good to go.

The market for synthesizers/grooveboxes has literally exploded in the last 10 years.

I came across the LMN 3: there’s a lot to unpack but it might be the most mature project in terms of both hardware and software out there. It’s as close to having the right tools, PCBs, etc. for an open source Teenage Engineering OP-1:

https://www.synthtopia.com/content/2022/06/25/the-lmn-3-an-o...

Look at Bela and Electro-smith Daisy, there are a bunch of simple diy synths made with teensy and some minimal components

https://bela.io/ https://www.electro-smith.com/daisy