InstrumentLIBRARY
A compact white and grey keyboard-style instrument with mechanical keys, four knobs and a small screen
Photo: Stone Preston (Fundamental Frequency), from the LMN-3 build guide on GitHub (credited and linked; not under a Creative Commons licence). Resized and converted to WebP.
Electronic · Groovebox Other DIY

LMN-3

An open-source groovebox with 45 mechanical keys, a screen, encoders and a joystick, running its own synths and sequencer on a Raspberry Pi

Designed by Fundamental Frequency (Stone Preston), published on GitHub

CC BY-SA 4.0 (PCB and case); code GPL-3.0 Commercial use OK Build info 5/5

Licence verified on GitHub, 21 October 2026.

Get the plans on GitHub ↗ Watch the overview
Build type
Electronics; the case is laser-cut acrylic layers
Difficulty
Medium-hard: through-hole soldering, flashing firmware, Linux setup
Controls
45 mechanical key switches, 4 encoders, a joystick and a HyperPixel 4 screen
Inside
Raspberry Pi 4 (tested on the 4 GB model) and a Teensy 4.1
Licences
Circuit board and case CC BY-SA 4.0; DAW and firmware GPL-3.0

About the LMN-3

The LMN-3 is a small, self-contained music workstation: a box of mechanical keyboard keys, knobs and a screen that runs its own DAW (built on the Tracktion engine) with synths and sequencing. Fundamental Frequency (Stone Preston) published everything on GitHub: the circuit board, the case, the firmware for the Teensy that reads the keys, and the DAW that runs on the Raspberry Pi.

The build guide has the full parts list and a photo walkthrough: flashing the Teensy firmware from a Linux computer, soldering the diodes, key switches, encoders, joystick and Teensy, and stacking the layered case. You order the board from the published Gerber files at any PCB maker. The case is acrylic layers you can laser-cut yourself or send to an online cutting service; keycap icons print on sticker paper.

The repos haven't changed since 2023, so treat it as a finished, stable design rather than an active project.

Who it's for. Makers comfortable with soldering and the Linux command line who want a portable, hackable music box. This page summarises the build guide; we haven't built one ourselves.

What you'll need

Materials

  • 4 acrylic sheets (12 × 16 × 1/8"), if you laser-cut the case yourself

Bought parts

  • A Raspberry Pi 4 (4 GB) and a 15 W USB-C power supply
  • A Teensy 4.1
  • A Pimoroni HyperPixel 4 screen
  • 45 five-pin mechanical key switches and keycaps
  • 49 × 1N4148 diodes
  • 4 × EC11 rotary encoders and a joystick
  • The LMN-3 circuit board, ordered from the published Gerbers
  • Header strips, a micro-USB cable, M2.5 bolts and nuts, rubber feet
  • Clear sticker paper for the keycap icons

Tools

  • A soldering iron
  • A Debian-style Linux computer with VS Code and PlatformIO
  • A laser cutter or an online cutting service
  • A laser printer for the icons

Build overview

Our own outline of the build guide.

  1. Order the board and case. Send the Gerbers from LMN-3-ECAD to a PCB maker, and the case files from LMN-3-MCAD to a laser-cutting service (or cut them yourself).
  2. Flash the Teensy. Build and upload the firmware with PlatformIO in VS Code, adding the udev rule on Linux.
  3. Solder. Fit the diodes and Teensy, then the key switches (seated through the acrylic switch layer), encoders and joystick, checking as you go.
  4. Add the keycaps and build the case. Print the icon stickers, fit the keycaps, and stack the acrylic layers with the bolts.
  5. Set up the Pi. Set up the Pi with the LMN-3 DAW and configure the HyperPixel screen, following the guide.

Video

Play video: Overview (loads YouTube)
Overview, Fundamental Frequency (the designer). Plays from youtube-nocookie.com after you click.

Nothing loads from YouTube until you press play. Video thumbnails are © their creators.

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