Nick Indge, writing at Ars Technica, bought an M-Vave FM-1 for $59.72 and found an active custom firmware scene already built around it. The FM-1 was sold as a pocket take on the Yamaha DX7, with 27 soft-touch piano keys and a 1.54-inch TFT display. In July, people on Reddit’s r/synthdiy began reverse-engineering the stock firmware. Custom builds started showing up in September.

On October 17, M-Vave responded by releasing FM1 Open: an SDK, a browser-based workbench, and stock firmware v15 as an open platform, with the application source under GPLv3 and an in-browser emulator for testing before flashing. The synth engine itself is still a closed binary, so only the application layer is open.

Indge tried several community builds. Melodee adds CZ-1, DX7, drum, and Commodore 64 SID engines. Felucca runs more than a dozen engines at once with a sampler and a pattern sequencer. SLOOP turns the unit into an eight-track battery-powered groovebox. And yes, it runs Doom.…