The Open Woodwind Project

An Electronic Aerophone with focus on usability as an instrument.

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An Electronic Aerophone with focus on creating an intuitive human interface for musicians playing real music.

Latest Demo:

Official Entry Video:

What is the Challenge this Project Addresses?

Many engineers, hackers, and makers have focused on the hardware implementation of creating a musical gadget of some kind. The challenge is that most of these instruments are heavy on hardware and light on usability as an actual instrument. 

In the digital instrument market today there are very limited options for MIDI woodwind controllers. This project aims to bring a DIY opensource version up to the plate that the average maker can create and play. This could eventually be a great project in school curriculum for those technologically inclined musicians beyond the standard robot classes.

We are flooded with MIDI keyboards, matrix controllers, drum sets, but those who wish to harness the dynamic response of breath are left lacking in options. This open source instrument should be a source to many hackers who would like to implement an intuitive and configurable instrument.

In the end I wish to offer up kits (laser cut files and pre-programmed microcontrollers) to those who would like to build their own instrument.

Project Goals:

    1. Create an electronic aerophone (MIDI woodwind controller) that is intuitively playable.
    2. Easily re-created by the average maker and is not just a music making gadget.
    3. Inexpensive and easily adaptive to new sensors and fingering modes

What is an Electronic Woodwind Controller?

Electronic instruments, and even MIDI instruments have been around for decades now, but usually you see developments in keyboards, drum pads, and matrix controllers. Several companies have made woodwind controllers to include Yamaha, Roland, and Akai, all stemming from the original concepts from pioneer Nyle Steiner. The EWI (Electronic Woodwind Instrument) and EVI (Electronic Valve Instrument) were the products of Mr. Steiner's genius. Akai still produces instruments from the original concepts introduced in these first designs.

Modern day computers have provided MIDI controllers a vast powerhouse for synthesis and sound design that can't easily be reproduced by stand alone instruments.

Nearly three years ago my first prototype was born, and recently the project has been picked back up to drive it to completion. This project is creating an Electronic Aerophone as a variation on the EWI, and will be released to the community once development has reached an adequate level of completion.

The following attributes are unique to this project, and help bring this controller to a new level:

  • Custom fingering mode, specifically designed to combat the 'glitch' issue of the Akai EWI
  • IMU integration for modulation and pitch effects
  • Analog outputs for Eurorack Systems

Technical Details

The controller itself utilizes a Cortex M4 microcontroller board (the venerable  Teensy 3.2 from PJRC), two MPR121 touch controllers (24 total channels of capacitive touch capability), an MPX2010GS pressure sensor,  an OLED screen, and some other various discreet components. 

Sensor data is fused together and sent via a MIDI stream to a computer for sound generation, or actualized into audio via the onboard synthesizer (currently a DSP-G1, but will probably change)

Code is released under the GPL.

Interesting Project Logs

Current Status

  • Second Prototype - 95% complete - Playable 
  • Designing laser cut files for final instrument design

OpenWoodwind Analog Patch.cmb

Reason combinator patch

cmb - 104.62 kB - 10/21/2018 at 20:42



Main source file, early working version

ino - 12.25 kB - 09/08/2018 at 04:20



C file for naming the USB iteration

C Source File - 253.00 bytes - 09/08/2018 at 04:15


  • 1 × Teensy 3.2 Microcontroller
  • 2 × MPR121 Semiconductors and Integrated Circuits / Misc. Semiconductors and Integrated Circuits
  • 1 × MPX2010GS Sensors / Pressure, Force
  • 1 × BNO055 IMU 9-DOF IMU
  • 2 × 1 kOhm Resistor

View all 9 components

  • Teensy 4.0 Audio Library Demo

    J. M. Hopkinsa day ago 0 comments

    The new microcontroller came in, and this time the real 'onboard' synthesizer is being demonstrated. The Pi will probably still be on the base station, but this synth will run directly on the microcontroller, without the need for external anything.

  • Update

    J. M. Hopkins3 days ago 0 comments

    Final Designs

    So I have finished the final 3D CAD files, and printed out the body. I'm having the keys cut out of carbon fiber, and then I have a bunch of prep work (sanding, filling, painting, veneering) ahead of me to to turn the 3D printed body into a 'final' instrument.

    I'll be dropping all new electronics in this instrument, but basically the same setup. Teensy 4.0 with audio shield this time, and wireless MIDI, but the basics will be the same. Two MPR121s, pressure transducer and accelerometer/IMU.

    Stay tuned!

  • ALSA Modular Synthesizer on a Raspberry Pi

    J. M. Hopkins4 days ago 0 comments

    In this quarantine I've also been able to play a bit with using a Raspberry Pi as a sound source. Using the ALSA Modular Synthesizer I've got this patch going:

  • A Quarantined Small World

    J. M. Hopkins03/28/2020 at 01:08 0 comments

    Stay safe through these crazy times!

  • 3D Printed Body

    J. M. Hopkins03/05/2020 at 00:05 0 comments

    Been a while since an update, so I apologize! Starting to CAD up the body, and printing prototypes with PETG.

    Final construction will be sealed, sanded, painted, and looking pretty.

    Keys will be metal the holes are just for M3 fasteners.

  • Onboard Synth Development - Teensy Audio Library

    J. M. Hopkins11/18/2018 at 04:00 0 comments

    The Teensy Audio Library is pretty amazing. 

    It allows for 16-bit 44.1kHz audio from a microcontroller. I'm using it to develop a synth onboard that doesn't make you want to cringe.

    Here's the block diagram:

    The hardest part of the synthesizer is the effort to smooth out the amplitude changes and pitch bends. Take a listen to these samples:

    All sound is produced onboard the synth, including the reverb. I'm still actively developing the code base, but so far so good!

  • Onboard Synth Work

    J. M. Hopkins11/01/2018 at 01:16 0 comments

    I want an onboard synthesizer for computer free playing, but along with pitch bends.

    Utilizing an ATtiny85 for some onboard synth development:

    The sound is an analog chorus sound (juno ish) with a decent low end and allows for 1V/octave input through 5 octaves.

    Listen here:

  • Reason Synthesizer

    J. M. Hopkins10/21/2018 at 20:41 0 comments

    Most of the time I use Reason as my main synthesizer while playing. I'm including my analog synthesizer patch in the files section. Even those with other woodwind controllers should easily be able to use this patch to create great sounding music. 

    Reason offers a free 30-day trial, but even after that, you can load the patch and play live without issue (just can't save files from the DAW). Free Reason Trial

    Great synth station for keyboards and live audio as well!

    There will be some rack extensions that you need to install also, so hit me up if you need some help with this.

  • Schematics

    J. M. Hopkins10/21/2018 at 20:25 0 comments

    The actual schematics for this project are super simple. Three breakout boards and a Teensy 3.2 were used. 

    Originally a lower power microcontroller was used, as nothing in this project really requires the Cortex M4 or advanced feature set of the Teensy 3.2. However the project was transitioned over to this development board in the hope of one day creating a great sounding synthesizer on the same chip. 

    Breakouts for the MPR121 and BNO055 were used because I had them handy, but when the kit is developed I plan on having them native to the PCB. While MPR121s are at end of life, they are still readily available, and if become hard to source it would be easy to switch to another capacitive touch IC.

    This schematic does not show the wireless serial connection, but for those who have an amateur radio license in the US, they can utilize the APC220 which is a really superb option for this project.

    My prototype also has two pull-down resistors on SDA and SDL, but were not needed when using the breakouts from adafruit, but add them in if you are having trouble with your I2C.

  • Preparing for the Hackaday Prize!

    J. M. Hopkins10/19/2018 at 02:10 0 comments

    We were lucky enough to get this project into the semifinals of the 2018 Hackaday Prize!

    Because this was the last of the 5 challenges it means that I now only have a few days to prepare for the final round... 

    There is a list of things that I need to do for you guys and not a lot of time (particularly with my work load here at SpaceX).

    1. Write up a full schematic / block diagram of the hardware

    2. Draw an updated flow chart of the state machine

    3. Show block diagram of the Reason Synth (and upload to files)

    4. Write build instructions 

    5. Write initial checkout / power on procedure

    6. Last but not least, make a new 2-5 minute video better describing my project.

    Peace of cake.

View all 33 project logs

  • 1
    Prepare Instrument Body

    Cut two pieces of hobby grade plywood into rectangular pieces, 2"x20", drill holes for furniture tacks and body spacers

  • 2
    Solder Main Board

    Solder Teensy, IMU, pressure, and capacitive touch breakout boards to proto board. Attach board to main body, route tube to top of device, solder keys to the MPR121 touch inputs.

  • 3
    Flash Teensy

    Download and flash the .ino file to the Teensy

View all 5 instructions

Enjoy this project?



Michael Johnston wrote 5 days ago point

It's great to have you back.  I've created the hardware for a very similar controller based almost entirely on your design.  Thank you, so much for sharing what you've done.  I'm beginning the software development now.  Are you anywhere close to being able to share your source code?

  Are you sure? yes | no

J. M. Hopkins wrote 4 days ago point

The source code is shared above in the files section. The state machine is very solid, but the pitch bend and fingering functions are quite messy and pretty hard to follow. Most of the 'magic' of the instrument is actually in the IMU filtering, dampening, and gating, which was very 'by feel' over many days and fiddling. 

I also have a repository: that I just put public.

I have a teensy 4.0 that I have arriving here soon that I plan on doing some more DSP attempts with, bu the state machine and general code will be that from above, just with the Teensy audio library overtop.

The Raspberry Pi has also been very interesting recently as a sound source and price point. So we'll wee where we end up.

  Are you sure? yes | no

J. M. Hopkins wrote 4 days ago point

I've also just cleaned up and commented a bit... so hopefully it makes more sense (see github)

  Are you sure? yes | no

AlexC wrote 07/31/2019 at 18:29 point

Hi. I noticed that activity halted in late 2018. Is there going to be any more movement on this project? Also, from listening to your latest demos from teensy synth, I've imagined adding a 'chiff' or 'shiff' sound at the beginning of each breath to give it a more natural woodwind flute quality.

  Are you sure? yes | no

J. M. Hopkins wrote 03/05/2020 at 06:57 point

Hey sorry for like a 8 month lack in response, life keeps me busy. I've started work on the 3D printed body recently

  Are you sure? yes | no

sacha.elijah.duprez wrote 06/12/2018 at 16:42 point

Woah, just discovered what you're doing. I'm very surprised by the quality of the sound, especially concerning the low notes : I like it ! 

Do you plan to improve it again ?

  Are you sure? yes | no

J. M. Hopkins wrote 06/14/2018 at 03:19 point

Thanks man, yes there is still quite a bit of development going to take place.

  Are you sure? yes | no

Johan Berglund wrote 05/14/2018 at 17:21 point

Great to see you are picking this up again!

  Are you sure? yes | no

J. M. Hopkins wrote 05/15/2018 at 06:16 point


  Are you sure? yes | no

Johan Berglund wrote 06/06/2016 at 18:26 point


Thanks for your replies! Thinking of putting the dsp-G1 in my Casio horn if I get to modifying it. Then I won't be missing the pitch bend functionality, as it didn't have it to begin with :) Portamento will still be missed though... but then again I get a key free for other things, like a bis key perhaps. Anyway, thanks again, and I hope you get time to proceed with your Aerophone project soon!

  Are you sure? yes | no

pietkamps wrote 01/19/2016 at 20:31 point

Hi Hopkins, I am interested in how you made the bite sensor or what hardware you have used.

  Are you sure? yes | no

J. M. Hopkins wrote 01/20/2016 at 12:15 point

I've used simple FSRs mostly.

  Are you sure? yes | no

edil07 wrote 06/06/2015 at 20:30 point

Hi Hopkins, I am very interested in your work and thinking of implementing it during my vacation at work in case you have already released it as open source.
Have you considered using Moteino ( as the microcontroller since it provides wireless 

  Are you sure? yes | no

J. M. Hopkins wrote 06/06/2015 at 23:38 point

Hello, as of right now there's not been a release of code, but I can release some of it through my Open Woodwind Project.

There are a few microcontroller options with built in wireless, but I've opted to use separate devices for more flexibility in transceiver choices. 

  Are you sure? yes | no

Gwendolyn Scogin wrote 06/05/2015 at 17:36 point

I am curious as to what hardware you are using for the breath pressure sensor.

  Are you sure? yes | no

J. M. Hopkins wrote 06/06/2015 at 23:39 point

It's an MPX2010GS. I'm still developing this project, but just taking a bit longer than I was hoping for. Being active duty military with a family eats a lot of time. 

My software and hardware will all eventually be released as open source under the Open Woodwind Project, which I assume you'll find interesting :)

Also, I'm now using a Teensy as my primary microcontroller... Good stuff.


  Are you sure? yes | no

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