I’ve actually been building a few synths based on the Pi over the years—it’s been a great way to “get rid” of the older boards as time goes on, although since I’ve never bought a Pi 5 I suspect that time has past.

You can use the Pi 2/3/3a/Zero 2 to build things like an mt32 or DX7 emulator almost trivially, and they make for great DAWless modules.