Any other MIDI devices installed? Can you try with just Montage and all the other hardware unplugged?

Tried a USB hub between the Mac and Montage? I wouldn't suspect this would help anything - but is a HW vs. SW step.

Does Bluetooth have anything to do with MIDI (using a MIDI-over-Bluetooth device?) -- or is it just that Bluetooth is caught in the wake of this episode and otherwise doesn't seem to relate to MIDI and Montage?

I'm not that familiar with Mac - just getting the ball rolling.

I been having this same problem with the iMac (Retina 5K, 27-inch, Late 2015) macOS 10.12.4 and steinberg drivers V1.9.10 Problem occurs when your DAW is open and turn of the Montage. For instance if you close Cubase, Logic they do not fully unload or close you have to do a secondary closing of programs. If you do not your mouse, keyboard, bluetooth freezes. There is also another issue with the Yamaha Steinberg USB V1.9.10drivers. If your Montage is turned on first then you start your iMac the Audio part will load but the MIDI portion will not initiate you have to go to Audio MIDI setup and rescan to initialize the MIDI. I do not have this problem before I Updated to the latest Drivers V1.9.10

Jason, thanks but;

No other Midi devices installed.

Don't have a hub to try, but I doubt it.

No Bluetooth midi devices are being used or showing up in the "Audio Midi Setup" App.

Harold, thanks also but;

I have this problem whether I have Logic running or not.

With the previous computer I had to Power up the Montage a second time to ensure it was online in "Audio Midi Setup", but after that everything worked fine.

It seems to be a problem between the Yamaha Steinberg driver and OSX Core Audio.

I have found a workaround for the time being.

I have to go into the "Sound" preference pane and change the input and output sources back to the Mac's internal ones prior to Powering down the Montage. I never had to do this before, so I suspect it is to do with OSX Sierra and the Yamaha driver.

Maybe it will be fixed in an update to the Mac or to the Yamaha driver down the track.

Hope so. It's a pain in the arse at the moment.

Maybe I'm reading too much into the "bluetooth" part of your feedback and though perhaps the system is locking up - so nothing special about Bluetooth being unavailable as I was starting to theorize something.

No need to get a hub in my opinion because the hardware test case has already been tested by what you're doing (direct connect works fine as long as SW is configured in a particular way). ... not that you should have to.

Yamaha thinks they're golden with Sierra:

http://www.yamahaproaudio.com/global/en/downloads/firmware_software/compatibility/compatiblity_osx.jsp

Someone tell that team to regression test powering off the end device as a test case.

Here's a more detailed view of what was tested (well, more context at least - not more detailed for the Mac+Montage case):

http://download.yamaha.com/api/asset/file/?language=en&site=ae.yamaha.com&asset_id=57068

Hi Jason.

It's both Bluetooth and USB that freeze or fail to respond. I can't tell if the whole computer is frozen as without Bluetooth or USB I can't use a keyboard or mouse to try and check anything else. I also can't find any crash log for the event, which the Mac would normally generate.

I might start deleting some audio preference files and then reinstall the Yamaha driver later and see if that helps.

On Windows how I would check for a hard lockup vs. just keyboard being unresponsive would be:

1) Try to ping my computer from another device like my phone, another computer on the same network, etc. If no response chances are the computer is locked up. I'd use my router to figure out what my computer's IP is to ping.

2) Or (and easier) I would press the power button with a momentary press. Not a hold - just a quick push. If the computer doesn't start shutting down (responding to the ACPI power button request) - then the system is probably hard locked. This would mean only a long press (3-5 second hold) would do. I believe it's 10 seconds on a Mac.

You do say force a shutdown with a power button press - so maybe the system is "alive" and shutting down. Although not completely clear if this is a long press forcing the Mac to power off (and not "shut down" - as a process that closes files, etc) or the short-press shutdown that shows your system doing more video/etc. updates after the power press.

I understand this doesn't really help get to the end - but does help define the nature of the unresponsive system which may be helpful to narrow down the possibilities.

Note: some machines have a watchdog timer that, if not serviced, will restore the power button to a more direct power-off without making a request through ACPI. If this is true, then a short press will even make the computer immediately turn off - which would be different behavior than the expected shutdown process which shows some screen telling the user that the system is shutting down - and files saved - etc. before eventually the system shuts down after some delay (going through the full shutdown process).

Hi Jason, thanks for the ideas.

Under OSX Sierra the power button seems to work in 3 different ways.

Short press puts the computer to sleep, can be woken with another short press.

Longer press (5 secs?) brings up the shutdown option screen.

10 sec press forces a shutdown with no options.

I should have said earlier that when I have this problem the shutdown option screen does appear, but I have no way of selecting an option, which means I have to keep holding it down until it shuts itself down.

I guess this means that the computer is not fully frozen, but at least the USB and Bluetooth are.

You most likely have to find a way to remove the Yamaha drivers, Any components In Logic like Montage connect. Remove the component in Audio/MIDI setup MIDI studio remove Montage. reset iMac pram and SMC to clear out the system. After reinstall Yamaha drivers, if you still have the previous drivers use them see how they work.

Removing the Yamaha drivers you may need to get app cleaner then go to Macintosh Hard drive Application/Yamaha Steinberg usb control Panel drag it to App cleaner this should find all the associate files with it. look for the drivers and remove.

Like i said before I had similar problems with the drivers , also I have to reset the MIDI or remove the MIDI component in MIDI studio because I get hung notes on the D3 key of the Montage some times the Panic button In logic won't work. Maybe you can overwrite the Newer Yamaha drivers with the older or previous driver. What ever it is the Yamaha drivers caused some kind of corruption in you iMac.

Hi Harold, and thanks.

I've already done all of this a few times before, but just done it all again to make sure I didn't miss any files and preferences associated with Audio or Yamaha or Steinberg. I removed everything I could find and searched for hidden files as well.

I then reset the SMC and NVRAM / PRAM.

I've tried an older driver (V1.9.9) before, but that caused a Kernel Panic, as Yamaha have warned.

So I reinstalled the 1.9.10 driver again, and still have exactly the same issue. All USB and Bluetooth connectivity is lost if I switch off the Montage whilst it is selected as the Input/Output source for the Mac. It should just default back to the internal Speaker and Mike for input / output, and not freeze anything.

Anyway, I've given up for the time being, and just try to remember to manually switch input / output whenever I use or shutdown the Montage.

I think I've finally found the problem.

I had the Piano Marvel app installed (Piano Training Software). This has a plugin as part of the app.

This plugin and the Yamaha/Steinberg USB driver do not seem to co-exist well. Un-installing either of them, but not necessarily both, solves my problem.

So for the time being given that I need the Yamaha driver to use the Montage with Logic Pro, the Piano Marvel plugin has been removed till I need it again.

I have the same problem. I have to close GarageBand first before shutting down my mx49