Demo / Features / LinnStrument settings / Hardware / Software / State of the project

Teensy Headless MPE Synth

This is a sound synthesizer for the Teensy microcontroller.

The goal of this project is to build a small and portable MPE synth as a companion for the LinnStrument MIDI controller. This fulfils my need of being able to jump in a short practising session while comfortably reclining in the couch or breathing fresh air in the park, leaving my computer with at home.

Prototype demo!

This prototype is built with development convenience in mind. The components could easily fit in 1/3 the volume for maximum portability.

Synth in wooden box!

Full LinnStrument setup powered by power bank:

Demo song (turn up video player volume)

Demo.song.mp4

Slide and loudnes

Slide.and.loudness.demo.mp4

Features

• It implements the MIDI Polyohonic Expression Specification (MPE for short).
• The synth is headless, meaning that there is no physical source of input like buttons or knobs. The synth is entirelly controlled by MIDI.
• Polyphony with a configurable number of voices.
• The MIDI is delivered by the synth by a USB port.
• The synth has USB-host capabilities. It can power MIDI controllers connected to it.
• Jack 3.5 audio output.
• It can be powered by regular a USB powerbank for portability, so you only need the powerbank, the synth, a MIDI controller and your headphones :-)

LinnStrument recommended settings

Configure your LinnStrument like this to get the most out of the synth:

• MIDI Mode: ChPerNote.
• PerNoteChs: All 16 channels.
• Bend Range: 24.
• Pitch/X: ON.
• Timbre/Y: ON.
• Loudness/Z: ON.

Hardware

Shopping list

If you want to build your own, you'll need:

• Teensy 4.1. Will probably work with Teensy 4.0.
• Teensy Audio Shield.
• An USB type A female socket.

Build

No schematics needed! Just

• Connect the audio shield to the Teensy (instructions on the pjrc site).
• Connect the USB type A to the Teensy (check the Teensy pinout to see where it goes).

Loading the software

This can be done using the Arduino IDE after installing some Teensy plug ins. There are plenty of tutorials out there.

Software

The project is divided into 3 files:

• mpe-synth.ino: Arduino sketch file, defining the loop and setup functions. Here the synth is configured and the incoming MIDI messages are passed to the actual synth. If you want to modify the info sent to the synth, edit here.
• Synth.h: contains the synth code, that handles MIDI messages and forwards them to the corresponding voice. If you want to change the behavior of the synth, edit here.
• Voice.h: Here is the code that produces sound for each of the voices. For now, just a simple waveform. If you want to change how the synth sounds, edit here.

State of the project

This is not finished, but it is in a working state that fulfills my needs. I don't feel like continuing development since I have higher priority projects right now.

Collaborators and feedback are welcomed! I would love to hear your comments. If this is useful for other people I may feel the urge to continue working on this.

Planned features

Not yet implemented and they probably won't be:

• Control Synth parameters via CC messages.
• Implement some sort of sound generation better than a simple waveform per voice like it is right now.
• Make sound respond to the Timbre/Y dimension.

Thanks

Thank to ghostintranslation for its SimpleSynth code which has greatly inspired this!

And of course thanks to Roger Linn for designing this amazing interface :-)