Convert a toy piano to work as a midi device and use it with Synthesia using Arduino

toy piano

Goal of this project:
Convert a cheap toy piano to work as a midi device and use it with Synthesia (
Other programs that use midi inputs can also be used.

 toy piano

The pushbuttons of the piano are used to make a simple pull-down circuit for the arduino mega. The arduino interprets the keystrokes and sends serial midi data to the pc. Then this data is send to a virtual midi port with “serial-midi converter”. This midi port is connected to Synthesia via “MIDI Yoke”. MIDI Yoke is a driver that creates virtual ports. Each port has an input and an output which are connected. With MIDI Yoke you can couple different midi programs without any physical hardware.

Step 1: Parts and tools

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List of the parts needed for this project:

– Toy piano
– Arduino mega (This project van also be done with an arduino uno but you should use an line decoder to expand your arduinos inputs.)
– Flat ribbon cable (from old pc)
– Connectors (1 for piano and 1 for arduino)

List of tools needed:

– Soldering iron
– Desoldering pump or wick
– Ohmmeter
– Hot glue or any other strong glue


Step 2: Hardware


The pushbuttons of the piano keys are used to make simple pull down circuits. The internal pull-up resistors in the atmega IC are used so we don’t need extra external pull-up resistors.

– Open the toy piano and locate the pushbuttons corresponding to the piano keys.
– Check if all the buttons have a common line. This is the ground line.
– Locate and remove the main IC. Solder wires to all leads going to the buttons including the ground wire.
– Check you didn’t make any shorts while soldering. (ohmmeter)
– Solder the other ends to the connector for the flat ribbon cable.
– Make a cutout in the housing of the piano for the connector.
– Reassemble the piano.

Step 3: Software

Arduino Code:
The arduino just checks all keys one after another and keeps repeating this. Every time a key changes its state (pressed or released), serial data is send which specifies: the action (pressed or released), the tone corresponding to this key and the velocity. The velocity is set to the maximum since the keyboard is not velocity sensitive.

It should also be possible to change other setting via midi. e.g.: change the pitch, change the instrument, … This is not implemented in my arduino code and i also didn’t check this.

MIDI Yoke: (
Just install MIDI Yoke and restart your pc. If everything went right you should find an icon named “MYokeNT” in the control panel.
You can specify the number of virtual midi port here. For this project you just need 1.

Read more: Convert a toy piano to work as a midi device and use it with Synthesia

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