Chiel Zwinkels

The Arithmophone x3 MIDI

*** This page refers to a legacy version of the Arithmophone Midi. For the latest version, please visit this page ***

You can use the Arithmophone as a MIDI controller for hardware and software instruments. This does come with some caveats: it works using Web Midi, which only some browsers and devices support. To make the most of it, you will also need a touchscreen device that is at least tablet-sized. I use a Microsoft Surface tablet myself and there it works great, running both the Arithmophone and the DAW/plugin it controls to provide a fully self-contained instrument. You should be able to get it working on other touchscreen devices that run Windows and potentially on Android / Chrome OS as well, although I haven’t been able to test this. It also works fine on a regular Mac or Windows computer. Without the touch screen you lose much of the immediacy but it can still be useful for sequencing and general experimentation. Here is how to get the Arithmophone MIDI up and running in 5 easy steps:


You will need to use a browsers that support Web Midi. I got the best experience using Opera, but any chromium-based browser should work (this includes Chrome and Edge). Web Midi is not supported in Safari and Firefox. It is also not supported on iOS/iPad OS (regardless of the browser you use). So unfortunately, MIDI is not an option on iPhones and iPads at the moment. You can still play the regular Arithmophone web app on these devices though.


Your browser will need to “see” at least one MIDI output. If you have more than one MIDI connection, that’s fine. You can select which one you want to use from the settings within the Arithmophone. If you have connected a hardware MIDI interface (or an audio interface with MIDI) to your computer, it should show up automatically. If you want to send MIDI from the Arithmophone to a DAW or other app, you may need to create a virtual port first. On Mac OS, this is done by opening the audio midi setup, then opening a midi studio window and activating IAC Driver. On Windows, you can achieve this by installing an app like Loop Midi.


You can use the Arithmophone x3 MIDI to control any MIDI compatible hardware or software instrument. However, to make full use of all the possibilities, you will need an instrument that supports microtuning. Not every MIDI instrument can do this, but there are many that can, including some some great free options.

For example, you could use the free Vital software synthesizer. This is a very flexible instrument and it also works in standalone mode, so you won’t need any other software to get started. If you’re working within a DAW environment, I recommend using the wonderful free plugin “MTS-ESP mini” from Oddsound. This will act as a tuning adapter between the Arithmophone and the instrument(s) you control with it. The Oddsound website contains a list of compatible software synths including some very nice free ones, like Whispair and Podolski. You can just add one of these plugins to your DAW and move on to the next step.


Each version of the Arithmophone needs its own tuning file. You can download these .tun files below and then load them into MTS-ESP Mini or directly into your instrument of choice. I’ve included files tuned to D for all versions, and one more tuned to a different key for each. If you want to play any of the Arithmophones in a different key, you can just transpose your instrument, or open the .tun file in a text editor and change the reference frequency. (It’s labeled “BaseFreq” and you can change it to any frequency you like, here is a list of frequencies for standard musical notes – make sure to save the new file with the extension .tun.)


You’re all set now, the next step is to open the MIDI Arithmophone of your choice. Clicking one of the links below will open the keyboard of your choice in a new tab. The downloadable Quickstart Guides explain all the functions within.

Arithmophone ToneHive x3 MIDI

ToneHive x3 Quickstart guide

Arithmophone Korale x3 MIDI

Korale x3 Quickstart guide

Artihmophone EDO x3 MIDI

EDO x3 Quickstart guide

This should be all you need to get started with the Arithmophone MIDI. For more details about the acoustic principles and design philosophy behind the Arithmophone instruments, please visit these pages.

This page is part of my Arithmophone project.
Arithmophone concept and design by Chiel Zwinkels © 2023