Might be useful to some:
https://github.com/gbevin/ShowMIDI

This application fills a void in the available MIDI monitoring solutions.

Instead of wading through logs of MIDI messages to correlate relevant ones and identify what is happening, ShowMIDI visualizes the current activity and hides what you don't care about anymore. It provides you with a real-time glanceable view of all MIDI activity on your computer.