Meowsic Keyboard MIDI Adapter Aims for Purrfection

Both small children and cats have a certain tendency to make loud noises at inopportune times, but what if there were a way to combine these auditory effects? This seems …read more

Jun 15, 2025 - 04:00

Meowsic Keyboard MIDI Adapter Aims for Purrfection

A black PCB is shown, with an Arduino Nano mounted in the bottom left corner. The rest of the space on the PCB is used up by ten DIP integrated circuits and a few resistors and diodes. Several black and red wires connect different parts of the PCB.

Both small children and cats have a certain tendency to make loud noises at inopportune times, but what if there were a way to combine these auditory effects? This seems to have been the reasoning behind the creation of the Meowsic keyboard, a children’s keyboard that renders notes as cats’ meows. [Steve Gilissen], an appreciator of unusual electronic instruments, discovered that while there had been projects that turned the Meowsic keyboard into a MIDI output device, no one had yet added MIDI input to it, which of course spurred the creation of his Meowsic MIDI adapter.

The switches in the keys of the original keyboard form a matrix of rows and columns, so that creating a connection between a particular row and column plays a certain note. [Steve]’s plan was to have a microcontroller read MIDI input, then connect the appropriate row and column to play the desired note. The first step was to use a small length of wire to connect rows and columns, thus manually mapping connections to notes. After this tedious step, he designed a PCB that hosts an Arduino Nano to accept input, two MCP23017 GPIO expanders to give it enough outputs, and CD4066BE CMOS switches to trigger the connections.

[Steve] was farsighted enough to expect some mistakes in the PCB, so he checked the connections before powering the board. This revealed a few problems, which some bodge wires corrected. It still didn’t play during testing, and after a long debugging session, he realized that two pins on an optoisolator were reversed. After fixing this, it finally worked, and he was able to create the following video.

Most of the MIDI hacks we’ve seen involved creating MIDI outputs, including one based on a Sega Genesis. We have seen MIDI input added to a Game Boy, though.