If you are new to CircuitPython, see Welcome to CircuitPython!
Adafruit suggests using the Mu editor to edit your code and have an interactive REPL in CircuitPython. You can learn about Mu and its installation in this tutorial.
Download the latest set of libraries for CircuitPython to match the version of CircuitPython you are running. There is one library package for CircuitPython 3.x, 4.x, and so on. Click the box below and download the library bundle to your computer.
Open the library Zip file and copy the following files/directories onto the CPX CIRCUITPY drive in a directory called /lib. This library is the one used by the programs:
adafruit_midi(must be adafruit-circuitpython-bundle-4.x-mpy-20190507.zip or later)
See the CircuitPython Libraries guide for additional details on how to add libraries.
This code has been tested on CircuitPython 4.0.0 rc1 and the adafruit-circuitpython-bundle-4.x-mpy-20190507 libraries.