Piano Hat Midi on Raspberry Pi 3

The midi library must be compatible, there's no earthly reason why it wouldn't be. So I suspect it's something else afoot.

On your Pi 2 setup, what happens if you type:

pip freeze | grep midi

Versus on your Pi 2.

It might be a conflicting midi package, like python-midi, installed which also uses the "midi" module name. So the fix might be:

sudo pip uninstall python-midi

Edit: @RogueM beat me to it :D Above speculative debugging left in for posterity. And just in case it's somehow useful.