Roland has an in-house club for makers. (Patreon)

I don't know if Korg or YAMAHA has such an in-house club, but Roland's in-house club is one of the most active DIY instrument making groups in Japan.

It's called the "R-MONO lab" and its members enjoy making creative instruments.

https://r-mono-lab.tumblr.com/

We can see their work at the Maker Faire.

Surprisingly, there are few synthesizer works, and most of them are electronically controlled instruments with mechanical mechanisms.

They also hold workshops for children to make musical instruments and contribute to the local community.