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Fixing an "Undefined External Error" in MIDI-OX

If you receive an undefined external error like this in MIDI-OX after selecting your controller and clicking OK in the MIDI-OX setup, try the following these steps to resolve the error.
DISCLAIMER: These steps require that you modify the windows registry. You should only do this if you understand that modifying registry keys other than the one specified below could cause irreversible damage to your system. Please read the instructions carefully and do not edit any other values inside regedit, unless you know what you are doing. Additionally, please remember to close MIDI-OX before proceeding with the steps below.
You may also wish to make a manual back-up of your registry, via steps provided by Microsoft here.


The Basics:

The Microsoft Registry Editor (regedit.exe) enables you to view, search for, and change settings in your system registry, which contains information about how your computer runs and interacts with hardware.

Different devices have different Globally Unique Identifiers (GUID). The GUID is a unique key consisting of letters and numbers used to locate a specific devices registry entries.  The key we are using later in this article is a GUID for various audio and video devices. 

The entry we will add to this key gives access to another driver to help your operating system communicate with your MIDI device.

Steps to follow:

  • 1.    Hold down Windows key and press the letter "R". This will open the Run window. Type in "regedit" and press enter to open the Registry Editor.
  • 2.    Press CTRL + F on the keyboard to open the search window. Copy and paste the following key in the “Find what” field, Ensure that there are no spaces leading or following the key: 4D36E96C-E325-11CE-BFC1-08002BE10318
  • 3.    You can confirm that the search has located the correct key because the "(Default)" value shows as "Sound, video and game controllers" (however it may also show as "Value not set"), also the "Class" will show as "MEDIA". If you haven't located the correct key, do not change any entries.
  • 4.    Right-click in the right hand pane in the blank space underneath the data and select "New" >  select "Multi-String Value".
  • 5.    Right-Click on "New Value" and select "Rename". Type in: UpperFilters  (case-sensitive, all 1 word).
  • 6.    Next, double-click UpperFilters and under "Value data:" type in: ksthunk (case-sensitive, all 1 word). Now click OK.
  • 7.    Click File > Exit to close the Registry Editor. Disconnect, then re-connect your MIDI device to the software again.