Mac OS X - Problems with MIDI devices after an update

I use a Mac, and after installing an OS update, one or more of my MIDI devices aren't communicating with the computer or are acting strangely.  What should I do?

When installing a major Mac OS update over an existing one (not using a clean install), or when using Apple's Migration Assistant to transfer files and preferences from one Mac to another, you will often run into trouble with drivers not working properly, authorizations being lost or corrupted etc. When files are mixed between systems, or are transferred to a system they weren't specifically intended or created for, difficulty is always a possibility.

The suggesions below may help resolve these symptoms.


If your MIDI devices don't work properly after an update or migration.

Often, after an update or migration, you will need to "refresh" certain MIDI devices. This is done quickly and easily in your Mac's Audio MIDI Setup.

  1. On your Mac, navigate to Utilities>Audio MIDI Setup
  2. Go to Window>Show MIDI Studio
  3. Make sure your MIDI device is unplugged
  4. After you've unplugged your MIDI device, click on it and choose Remove Device

  5. Plug your MIDI device back into your computer


If the above steps do NOT resolve your issue...

  1. Empty the contents of the following two folders by moving their files into to two new folders on your desktop:

    Macintosh HD > Library > Audio > MIDI Drivers

    Macintosh HD > Users > [Your User Name] > Library > Audio > MIDI Drivers

    Note: the second location above is hidden on Mac OS X 10.7 and above.  To access it see these instructions.
  2. These are the places where third-party MIDI drivers are stored. If they have become corrupt, or they haven't been installed correctly, removing them and starting over may help.
  3. Restart your computer.
  4. Try your MIDI device again.
  5. If the symptom has been resolved, you should...
    1. Reinstall each of these drivers by visiting the home page for the respective device manufacturers. Note, if your MIDI device is Class Compliant, it doesn't require any extra drivers to be installed.
    2. Find and download the latest drivers for the product(s), and install them.
    3. Confirm all of your devices now work properly, then trash the files you had moved from your MIDI Drivers folder to your desktop.


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