The Harmotron




Introduction: The Harmotron

The Harmotron is a musical instrument that makes sure that all the notes you play are harmonious.

It does this by letting you play the chords with your left hand. Depending on what chord is being played the melody buttons with change their note. These would be played with the right hand.

The device will act as a midi controller

Step 1: Getting Stuff

What you will need:


  • Arduino (uno)
  • preferably an extended micro usb cord
  • a base (I use a simple piece of wood)
  • 13 push buttons
  • wires
  • resistors


  • Arduino Software
  • a Digital Audio Workstation, Anvil Studio works fine
  • LoopMIDI
  • Hairless MIDI
  • The Arduino MIDI library

Step 2: Connecting Lots of Buttons to the Arduino

I started by gluing all the buttons on the plank, as shown by the layout above.

Then securing the arduino onto the board.

The buttons are connected to the arduino via wires, as shown in the diagram above. It's almost the same as connecting one button, just a bunch of times.

Step 3: Uploading the Code to Arduino

First you need to instal the Arduino MIDI library to your arduino software.

Then open the included code file. It's a bit messy but it works.

You can now upload the code to your Arduino

Step 4: Setting Up MIDI Software

Now you need to open up loopMIDI and Hairless MIDI.

LoopMIDI will work fine as is, but you will need to make sure that the Baud rate on Hairless is set to 9600.

Then you can already connect Hairless to your LoopMIDI midi out channel.

Open up your Digital Audio Workstation / Anvil Studio and find the MIDI settings. There you can select LoopMIDI as your MIDI input.

Step 5: Connecting Arduino to Everything Else

The final step is weird, but not that hard if you know what to do.

You need to make sure your Arduino is running and connected to your pc. Then go to your Arduino software and open up the 'Serial monitor' under 'tools', or via Ctrl+Shift+M.

Now close the serial monitor window. This way you open the serial port, but don't occupy it.

You can now select Arduino as the Serial input on Hairless MIDI.

Step 6: Make Music

Be sure to wow people playing your harmonic tunes!

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