OPN-1
OPN-1 is open-source firmware for the M-VAVE FM-1 keyboard.
- Custom firmware
- Stable
- High brick risk
- Reversible
This project hasn't been claimed by its maintainer yet, so its details come from the community. Is it yours? Claim it
OPN-1 2.0 turns the FM-1 into a patch-based synth for the Mega Drive / Genesis sound chips.
Use it with the web app: https://opn-1.putch.co.uk/ (Chrome or Edge). The web app now works only with OPN-1 2.x; for 1.x, the 1.0 page stays at https://opn-1.putch.co.uk/v1/.
What's new since 1.0
- A library of 128 FM patches in 4 banks of 32, kept in flash. PRESETS or a program change picks one. Your 1.0 sound set moves into bank 1 when you install.
- Fill it from VOPM
.opmfiles (such as the 2612.org packs) or a game's VGM songs, into the bank and slot you choose, and export a bank back to.opm. - Single, Layer or Split: one patch, up to six stacked on the keys (with the note, after a delay or on release), or a patch per MIDI channel.
- A patch editor in the web app that draws every operator's envelope, plays your changes on the FM-1 and saves to the patch's slot.
- Redrawn FM-1 screens: envelope graphs, an operator page, a setup page and a new SEQ screen. The version shows at power-on and on the GLO page.
- Songs can be played as MIDI in GenMDM mode, or saved as a
.midfile, alongside the exact streaming. In GenMDM mode the screen names the library patch a song is playing. - A normal MIDI layout by default: the patch on channels 1 to 6 and 12 to 15, square waves on 7 to 9, drums on 10, noise on 11. GenMDM's layout is still a setting.
Install
From the OPN-1 project folder (see the README for Windows, macOS and Linux):
python3 tools/fm1_install.py opn1-2.0.0.fwsc
To go back to 1.0 or the official firmware, install that instead, or use the FM-1 Firmware Hub.
Installing is at your own risk: see the disclaimer in the README.
SHA-256 of opn1-2.0.0.fwsc:
31b88c6fd4ec081ce85393977453e61ff86c6f545f10e7b1db2023986803675c
The package contains BSD-3-Clause and Apache-2.0 code; LICENSE and LICENSING.md are attached.
Before you start
- How hard is it?
- EasyWith Slipway.
- What you need
- A USB or MIDI cable
- Comfort with the command line
- A computer
- Can it break my device?
- Could leave your device unusable. It may void your warranty.
- Can I undo it?
- Yes. You can go back to the official software.
Did it work for you?
Did OPN-1 v2.0.0 work on your M-VAVE FM-1?
No reports yet for v2.0.0.
One-tap reports from owners. Bricked reports are checked before they count.
Compatibility
Devices: M-VAVE FM-1.
No compatibility information yet.
Getting started
From the project's README ("Getting started"):
Install the firmware on the FM-1, as in Installing the firmware below.
Open the web app in Chrome or Edge: . To run it locally instead (Web MIDI needs https or localhost):
cd web && python3 -m http.server 8000 # then open http://localhost:8000/
Fill the library. In the Library, drop .opm files (or a few VGM or VGZ songs from one game), tick the patches you want, pick a bank and a start slot, and press Send to FM-1. OPN-1 does not include any game music or patches; use files you have the right to use.
Play. Turn PRESETS to step through the patches. The web app's Help tab explains every button and knob on the FM-1, and what to do when something goes wrong.
Rescue: if the FM-1 ever fails to start, hold OCT- while switching it on. It starts the USB updater only, so a working firmware can be installed from there.
Risk and recovery
- Brick risk
- High
- Reversible
- Yes
- Voids the warranty
- Yes
- Requires opening the device
- No
From the project's README ("Getting started"):
Install the firmware on the FM-1, as in Installing the firmware below.
Open the web app in Chrome or Edge: . To run it locally instead (Web MIDI needs https or localhost):
cd web && python3 -m http.server 8000 # then open http://localhost:8000/
Fill the library. In the Library, drop .opm files (or a few VGM or VGZ songs from one game), tick the patches you want, pick a bank and a start slot, and press Send to FM-1. OPN-1 does not include any game music or patches; use files you have the right to use.
Play. Turn PRESETS to step through the patches. The web app's Help tab explains every button and knob on the FM-1, and what to do when something goes wrong.
Rescue: if the FM-1 ever fails to start, hold OCT- while switching it on. It starts the USB updater only, so a working firmware can be installed from there.
Releases
| Version | Name | Released |
|---|---|---|
| v2.0.0 | OPN-1 2.0.0Latest | 17 October 2026 |
| v1.0.0 | OPN-1 1.0.0 | 16 October 2026 |
Credits, license and support
- License
- GPL-3.0