Chiel Zwinkels

Arithmophone MIDI (version 1)

*** This page refers to a legacy version of the Arithmophone. The latest version can be found here ***

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 is unfortunately not supported on all browsers and devices. To make the most of it, you will also need a touchscreen device that is at least tablet-sized, which further limits your options. However, it works great for me on my Microsoft Surface tablet, 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. Here is how to get it up and running:

1. Browser

Browsers that support Web Midi include Chrome, Edge and Opera. It 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. Of course, you can still play the regular Arithmophone web app on these devices.

If your browser supports Web Midi, the next step is to open the MIDI Arithmophone of your choice. The following flavours are available on my CodePen:

Junior (hexagonal grid using 5-limit just intonation tuning and single octave keys)

ToneDiamond (diamond-shaped grid using 5-limit just intonation tuning and double octave keys)

ToneHive (hexagonal grid using 7-limit just intonation tuning and triple octave keys)

ToneBrick 12 (square grid using 12 tone equal temperament tuning and double octave keys)

ToneBrick 31 (square grid using 31 tone equal temperament tuning and quadruple octave keys)

By default, the first available MIDI output will be selected and MIDI channel 1 will be used. You can change this in the settings menu (open with button in top right corner). 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.

2. Instrument

The ToneBrick 12 keyboard style uses default MIDI tuning and can be used to control any hardware or software synthesizer that supports MIDI. The other keyboard styles use non-standard tunings. For these to work, you will need a tuning conversion file to translate the MIDI output from the Arithmophone into the correct pitches on your instrument. This isn’t support on every MIDI instrument, but fortunately there are some fantastic free options avialable.

I highly recommend the amazing Vital software synthesizer. You can use this in standalone mode and load the necessary tuning files. If you’re working within a DAW environment, I recommend using the wonderful – and 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 and some of those are free as well, like the excellent Whispair. Some hardware instruments, like the Korg Minilogue, will allow you to edit the pitch of each note individually, even though you cannot use .tun files with these. This is a bit more work, but the end result is exactly the same.

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 (there is no tuning file for the ToneBrick 12 because it uses default MIDI tuning). I’ve also included an Excel file with tuning tables for all Arithmophone versions that you can use to retune your hardware synth.

The MIDI Arithmophone contains sliders for ‘Bend’ and ‘Mod’. These simply control the standard ‘Pitch Bend’ and ‘Mod Wheel’ parameters. On the Arithmophone, the ‘Mod’ control is continuous, but the ‘Bend’ control moves in 3 discrete steps. This is in order to allow precise and instant switching between the center position and the (all the way) up and down positions. Try setting the pitch bend range of your instrument to 7, so you can jump up or down a perfect fifth from the center pitch, or to 12 so you can switch octaves. On the ToneBrick 12, because it uses default MIDI tuning, I have replaced the ‘Bend’ control with an octave switch, to allow easy access to a range of 7 octaves.

This should be all you need to get started. For more information about the details of each keyboard style, please consult the Arithmophone manual. If you’d like to know more about musical intervals and tuning schemes in general, I recommend my interactive guide to the building blocks of melody and harmony.

This page is part of my Arithmophone project.
Arithmophone concept and design by Chiel Zwinkels © 2022