Open-KeyPrec

Open-Sourced Electric Keyboard Percussion Instrument

Code   Build   Usage   License

About

Open-KeyPrec is an open-sourced, pressure-sensitive electric keyboard percussion (mallet) MIDI instrument. It has 61 keys, spanning 5 octaves of playing range from C2 to C7 like a standard Marimba. It also has a MIDI control panel with 16 buttons, 12 knobs (8 × 280° potentiometers and 4 × 360° rotary encoders).

The sensors are controlled by an ESP32 development board, and the output is converted into a standard MIDI device. You can use audio workstation softwares like GarageBand or Reaper (or open-source alternatives like LMMS, Zrythm, or Ardour) to simulate the sounds of all kinds of different instruments.

Code

Source code structure

• /src - PC driver written in Rust
• /firmware - ESP32 module firmware written in C++
• /circuits - Printed circuit boards
• /models - 3D-printable models

Toolchains & Environments Used

• EasyEDA: Web-editor for creating circuit boards
• FreeCAD: Software for designing mechanical 3D models
• CLion: IDE for Rust & C++
• PlatformIO: Firmware development toolkit

Pin Configuration

Pins	I/O (A: Analog)	Name
4	O	Mux Select for C2-B6
5	IA	Mux Input for C2-B6
1	IA	Input for C7
8	I	(Panel) Input for 4 rotary encoders
3	O	Mux Select for buttons and potentiometers
2	I	Mux Input for buttons
1	IA	Mux Input for potentiometers
3	O	RGB LED Control

Total ADC channels required: 7 Total GPIO required: 23

Build

Materials Required

!!!!!!!!!! TODO !!!!!!!!!!

Tools Required

• FDM 3D Printer (~$300 Ender 3 is fine)
• Soldering kit (iron, solder, flux)
• Wood Saw
• A computer

1. Order PCBs

!!!!!!!!!! TODO !!!!!!!!!!

Usage

Setup MIDI Device

!!!!!!!!!! TODO !!!!!!!!!!

Setup Audio Softwares

A MIDI keyboard doesn't make sound on its own. To actually play an instrument, you would need an audio workstation software and some VST sound sources.

Notation: 🍎 - macOS, 🪟 - Windows, 🐧 - Linux

Free Mallet Sound Sources

Built-in Sources

• GarageBand comes with marimba, vibraphone, and glockenspiel sound sources. It's free but macOS only and does not have VST support.
• LMMS comes with several mallet instruments.

External Plugins

Name & Link	Author	Platforms	Formats
Alto Glockenspiel	Steinberg	🍎 🪟	VST, AU
Marimbaphonic	Alan Vista	🍎 🪟	VST, AU
VibroMaster	Alan Vista	🍎 🪟	VST, AU
DSK Virtuoso (Celesta, Glockenspiel, ...)	DSK Music	🪟	VST

Unfortunately there aren't any free VSTs supporting linux that I can find. You have to use Windows for this one if you don't have a mac/hackintosh. If you found any additional VSTs, feel free to make a PR!

Other free VST Plugins: https://github.com/webprofusion/OpenAudio