Q: MIDI support in Sierra

I also have this problem and I'm surprised there is no outrage on the boards.

My MIDI function is not working on Sierra - and neither am I -

Roland A-88 here. Luckily I have a MacBook on El Capitan that I can use instead.

PS. Roland has its Sierra Compatibility page up. Appears to be a partial list. I expect they will add information over time.

https://www.roland.com/global/support/support_news/1609211012/

I have same issue, but with a generic midi adaptor that worked perfectly till now. Opening the AUDIO MIDI Setup/ MIDI Studio, when i click on re-explore MIDI, it appears, and the number of entries change to plus 2, but doesn't work and don't let me check the device enabled. If again I re-explore MIDI, the number of entries change to minus 2

So it seems the only solution will be downgrade to el capitan and wait for better times. BTW siri on my computer has proven to be pretty useless, so no worries about downgrading (except that is time consuming)