Two Commodore 64 SID chips as a synth, on the M-VAVE FM-1.

SID-1 is open-source firmware for the M-VAVE FM-1 keyboard. It runs an accurate recreation of the C64's sound chip, the MOS SID, twice over: six voices, three on each chip, with the 6581 or the 8580 to choose from. It turns them into a synth you play from the FM-1's own keys and knobs, or over USB MIDI.

Its patches work the way a C64 music player's instruments do, updated 50 times a second: an envelope and a waveform, a wavetable for drums, arpeggios and noise attacks, pulse width and filter sweeps, vibrato and hard restart. It holds a library of 128 of them in 4 banks of 32, starting with 16 factory patches. A companion web page edits and organises them, and pulls the instruments and sampled drums out of a C64 tune (.sid), then plays the tune on the FM-1 as MIDI.

The FM-1's SOUND page: SWEEP PAD's pulse wave, its filter and the main knobs The WAVETABLE page: ARP MAJOR's three steps The GLOBAL page: two patches layered

Features

An accurate chip. sid.c is a C port of Dag Lem's reSID 0.16, integer only, and matches it sample for sample in the tests, for both the 6581 and the 8580. Both chips run on the FM-1's own CPU, with optional 2x oversampling. reSID 1.0's more accurate filter needs megabytes of tables, more than the FM-1 has, so the port is of 0.16.
C64 instruments as patches. ADSR and waveform (with sync, ring modulation and the test bit), an 8-step wavetable that can play absolute notes (drums) or relative ones (arpeggios), a pulse width sweep, a filter sweep with its mode and resonance, delayed vibrato, transpose and fine tune, and hard restart.
The C64's filter, as it was. Each chip has one filter for its three voices. A filtered patch's note restarts its chip's sweep, as on a C64, and the FM-1 gives filtered patches a chip each where it can, so each keeps its own filter.
A patch library. 128 slots in 4 banks of 32, kept in flash. PRESETS on the FM-1 steps through them and a MIDI program change picks one. The page copies, moves, renames and empties them, and saves banks to JSON files and back.
Single, Layer, Split or Voices. Out of the box the FM-1 plays one patch, up to six notes at once. Layer stacks up to six patches on every note. Split gives each MIDI channel its own patch, for a sequencer or DAW. Voices makes MIDI channels 1 to 6 the six voices, one note each, the way a C64 tune plays them.
Edit on the device or the page. Nine knob pages on the FM-1 for the sound, the envelope, the pulse and filter sweeps, vibrato and the wavetable. The page's editor shows every field at once and plays changes as you make them. SAVE keeps the patch in its slot.
Patches from C64 tunes. Drop a .sid file (PSID or RSID, from the HVSC) on the page: it runs the tune on its own 6502 and finds the instruments it plays, ready to send to the library.
A tune's sampled drums. Many C64 tunes play drums by writing samples to the SID's volume register, a trick that works because the 6581 leaks a DC offset. The page finds those samples too and sends them to the FM-1's sample kit, played on MIDI channel 10 through the volume register in the same way. Heard on the 6581, as on a real C64.
Songs as MIDI. The page plays a tune on the FM-1 as MIDI in voices mode, each SID voice on its own channel with its instruments, slides as pitch bend and the drums on channel 10, or saves it as a .mid file for a DAW. Close to the original, not exact.
MIDI over USB or the TRS jack. By default the patch plays on channels 1 to 9 and 11 to 15, with the sample kit on 10. Pitch bend is 2 semitones each way, up to 24 with RPN 0.

The FM-1's screens



HOME: the waveform, the filter, the main knobs	ENV: attack, decay, sustain, release, drawn	EDIT: transpose, fine tune, filter, sync, ring, hard restart

FX: the pulse width sweep	FX again: the filter sweep	LFO: vibrato

ARP: the wavetable's steps	ARP again: where it loops	GLO: chip model, 2x, the part, the mode; the parts

ALGORITHM changes the waveform, the filter mode or a wavetable step's waveform, depending on the page. OCT- and OCT+ move the keys an octave. The footer shows the six voices: lit while a note plays.

The web app

The Library: Arkanoid's instruments and drum samples in Import, bank 1 on the FM-1

Library: import a .sid tune, tick its patches, pick a bank and slot and send them, with its drums for the kit. Play the song on the FM-1 or save it as a .mid.

The Editor: a patch's sound, envelope, sweeps, vibrato and wavetable

Editor: pick a patch, change it and hear it on the FM-1 as you go, then save it to its slot.

The Setup tab: two patches split across MIDI channels 1 and 2

Setup: Single, Layer, Split or Voices, each part's patch and channel, and which part the FM-1's keys play.

Getting started

Install the firmware on the FM-1, as in Installing the firmware below.
Open the web app in Chrome or Edge: https://sid-1.putch.co.uk/. To run it locally instead (Web MIDI needs https or localhost):
```
cd web && python3 -m http.server 8000          # then open http://localhost:8000/
```
Play. Turn PRESETS to step through the 16 factory patches in bank 1.
Add patches. In the Library, drop a .sid tune, tick the patches you want, pick a bank and a start slot, and press Send to FM-1. SID-1 does not include any C64 music; use files you have the right to use, such as those of the High Voltage SID Collection.

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.

Installing the firmware

You need the FM-1 plugged in over USB and Python 3. The commands below run from the SID-1 project folder:

Get the project: Code > Download ZIP on GitHub and unzip it, or git clone https://github.com/putchdev/sid-1.git.
Download the .fwsc from the latest release into that folder, or build one (see Building and testing). In the commands below, use the name of your file.

Close anything else that talks to the FM-1 over MIDI first, including the SID-1 page and any DAW. On Windows only one program at a time can use it.

Windows. Install Python from python.org, ticking "Add python.exe to PATH". Open Command Prompt in the project folder and run:

py -m pip install mido python-rtmidi
py tools\fm1_install.py sid1-1.0.0.fwsc

macOS. Install Python from python.org (or brew install python). Open Terminal in the project folder and run:

python3 -m venv ~/.venv/fm1
~/.venv/fm1/bin/pip install mido python-rtmidi
~/.venv/fm1/bin/python tools/fm1_install.py sid1-1.0.0.fwsc

Linux. On Debian or Ubuntu:

sudo apt install python3-mido python3-rtmidi
python3 tools/fm1_install.py sid1-1.0.0.fwsc

On other distributions, use the macOS commands (Python's venv module may be a separate package).

The installer asks before it writes anything. The FM-1 then restarts into SID-1, shows its version on the screen and appears to the computer as SID-1 FM-1. tools/fm1_install.py --info shows what the connected FM-1 runs. If an install is cut off, run the same command again and it finishes.

SID-1 keeps its library in a part of the flash OPN-1 does not use, so switching between the two keeps both. To go back to the official firmware or another one, use the FM-1 Firmware Hub in Chrome or Edge.

Building and testing

You need Python 3 with Pillow, the JieLi toolchain and the AC79 SDK (see tools/get_toolchain.sh and build.sh), and a C and C++ compiler for the tests. The tests that use C64 tunes or other references look for them in build/ref and say what they skipped.

./build.sh                          # -> build/sid1.fwsc, identity FM-1_960
tests/run_sid_compare.sh            # sid.c against reSID 0.16, both models; also rewrites sid_tables.h
tests/run_store_test.sh             # the library's flash store
tests/library_test.py               # the page's MIDI protocol (docs/MIDI.md)
tests/parts_test.py                 # parts: channels, voices mode, pitch bend, filters a chip each, kept
tests/digi_test.py                  # the sample kit on channel 10, through chip 1's volume register
tests/web_app_test.py               # web/index.html in headless Chrome, against a fake FM-1
tests/c64_test.js [tune.sid ...]    # the page's 6502, CIA and .sid runner, PSID and RSID
tests/extract_test.js [tune.sid ...]  # the page's patch extraction, against the FM-1's own player
tests/song_test.js [tune.sid ...]   # the page's tune to MIDI, played on the FM-1's own player; its drums as samples
tests/run_host.sh [script.txt]      # the app on this computer -> build/host/sid1.wav and its screens
python3 tools/gen_font.py PressStart2P-Regular.ttf   # rewrites firmware/gen/felucca_font.h (the font: Google Fonts)

Disclaimer

Installing SID-1, or any custom firmware, on an M-VAVE FM-1 is done entirely at the owner's own risk. It may void the device's warranty, and an interrupted or faulty install could leave it unusable. SID-1 is provided "as is", without warranty of any kind (see sections 15 and 16 of the licence). Its authors accept no responsibility or liability for any damage to, or loss of use of, any device, or for any other loss arising from installing or using it. If you are not comfortable with that, do not install it.

Built with AI

SID-1 was developed with the help of AI: much of its code, tests and documentation were written by Claude (Anthropic) under the author's direction, then reviewed, tested on a real FM-1 and released by the author. It may still contain mistakes; reports and fixes are welcome.

Documentation


docs/MIDI.md	The full MIDI protocol: playing, parts and voices, the sample kit, the library, the patch's bytes
docs/RULES.md	The FM-1 chip's rules and what the build checks for
docs/API.md	What the platform layer gives the app

Credits

SID-1 stands on the work of others:

Dinghy by zvenson: the firmware base, host mode and build checks.
Felucca by Leo Kuroshita (Hügelton Instruments), with the changes of SLOOP by isod89: the FM-1 platform (boot, USB, updates, audio, panel).
reSID by Dag Lem: the SID emulation that sid.c ports, and the reference in the tests.
Klaus Dormann's 6502 functional tests and Tom Harte's per-opcode tests: the references for the page's 6502.
The Press Start 2P font by CodeMan38, and VT323 by Peter Hull.

Licence

GPL-3.0-only: you may use, study, change and share SID-1, and whoever receives a firmware built from it must be able to get its source. The SID core is GPL-2.0-or-later, and third-party parts keep their own licences; see LICENSING.md.

SID-1 is an independent project. It is not made, endorsed or supported by Commodore's owners, M-VAVE, or the authors of the projects above. Commodore 64 is a trademark of its owners; M-VAVE and FM-1 belong to theirs.