MIDI + Mini Piano

Recently I came across an Electron Echo Mini Piano that my brother and I played with many years ago:

I have no idea who made it or where it came from. The interweb mentions it a few times, but there doesn’t seem to be any information about it.

A moment of inspiration hit, and I decided it would be neat/fun/educational to build it into a sort of glorious MIDI-controlled monophonic electronic tinny-sounding synthesizer.

Opening the case revealed that each button simply connects a pin on the controller chip (under the black blob) to the positive side of the batteries – there isn’t even a matrix, unlike most music and computer keyboards.

I soldered 30AWG wire-wrap wire to each trace, labeling them with the solfège names printed on the keys so that I could connect them in the correct order. Then I connected the wires to a microcontroller and programmed it to play a simple tune.

With the proof of concept done, I moved on to the next step.

It turns out that reading MIDI using a microcontroller is very easy. I used the circuit and code (with a little modification) from here to read MIDI signals from my keyboard and turn on LEDs.

The final step was to combine the two circuits into one MIDI-controlled, Arduino-powered, piezo-speaker-somethinged monophonic synthesizer:

The fun in this project was in building it and seeing it work, rather than in having it once it’s done. I would be just disassembling it to reuse the parts, but in this case my cousin (who makes electronic music) is interested in it, so I’m going to rebuild it on perfboard in a proper case, with a jack for audio output, and maybe some interesting stuff to use up the remaining four pins on the microcontroller. More on that later.

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