So, you have a MIDI keyboard you want to use. But to get it working on this addon requires a few extra steps.


First we need to download a module that allows Garry's Mod to work with MIDI devices. We are going to use gmcl_midi. It's a free, open source project, and you can download ready-for-use files here:

https://github.com/FPtje/gmcl_midi/releases/tag/v0.2.0

On that page, under Assets, you will see two files. Click on:

• gmcl_midi_win64.dll if you downloaded the Chromium Beta for Garry's Mod, or;
  
• gmcl_midi_win32.dll if you have not opted to any beta programs (This is how Garry's Mod is by default)

After the download, Windows might warn you that the file is dangerous. This is not a widespread software after all, and it's nothing to worry about. Also, if it doesn't work after following all steps on this guide, try to right-click the file you downloaded, click on Properties, check Unblock, and click OK.


Make sure the game is not running. Then:

1. Open your Steam Library
   
2. Right click Garry's Mod, and click on "Properties..."
   
3. Click on "Installed Files"
   
4. Click on "Browse...". A window should appear.
   
5. Open garrysmod > lua
   
6. If it does not exist already, create a folder and name it bin
   
7. Open bin
   
8. Finally, move the file you downloaded to the bin folder

In game, if everything went right, the button under the Musical Keyboard settings should either say "Choose MIDI device..." or "<no devices detected>", if you have not connected any yet.