Hanz Electronics has made a cool MIDI Adapter to work with the Pocket Operator music devices.

Using a Teensy 3.6 and held in a custom 3D printed case this adapter uses pogo pins to make contact with the exposed button pads on the Pocket Operator allowing you to trigger all 23 buttons via MIDI.  It also has an internal digital polyphonic synth loaded with features.

This convenient adapter is available on Tindie and  the source code is available on GitHub.