Guitar

MIDI_KeyMap is a built in Reaper plug-in, helpful when you want to remap instrument keys (for example to map your electronic drums with a VSTi like Addictive Drums).
To define a map you edit a txt file that you then open with the plugin.

• In Reaper load MIDI_KeyMap and your VSTi to the fx stack of the same track
  Note: order matters, MIDI_KeyMap must be on top of Adictive Drums. This way, for example, when a C1 key is played the plug-in will remap it and send for example an E1 to Addictive Drums.
  
  
  
  After the plug-in, load Addictive Drums
  
  ---
  
• Find where MIDI_KeyMap txt map files reside:
  Inside Reaper go to: "Options" -> "Show REAPER resource path in explorer/finder..."
  
  This will open a explorer window where Reaper plug-ins are installed.
  In my case this was "C:\Documents and Settings\_Tero_\Application Data\REAPER"
  
  From this Folder, open the "Data" then the "ix_keymaps
  You are now at: "C:\Documents and Settings\_Tero_\Application Data\REAPER\Data\ix_keymaps"
  ---
• Make a copy of the MIDI_KeyMap existing map file "00 - Default Mapping.txt" and open it with notepad.
  You'll use this txt file to remap the keys (changing the first column numbers according to your edrums and your software).
  ---
• Untill you have all the keys perfectly remapped you'll have to:
  Edit the txt file (in notepad);
  Save it (in notepad);
  Reload it on the plugin (in Reaper);
  
  ---
  
• Your edrums will now sound correctly.
  But if you remove the plugin from the FX stack it will sound wrong again.
  
  In other words: your midi file was recorded with the wrong map. When playing this midi file, MIDI_KeyMap remaps it (converts) before reaching Addictive Drums where it will sound correctly.
  
  If you want to permanently convert your recorded MIDI file to the correct keys you can follow this steps:
  
  1. Remove the Addictive Drums from the previous track ("1. edrum recorded") so that it has only the MIDI_KeyMap enabled on the FX stack.
  2. Create a new track ("2. midi remap"). 
  3. On "2. midi remap" load Addictive Drums to the FX stack and arm it for record;
     
  4. On "2. midi remap" configure the input/output so that: the input of this track will be the output of the other track (so it will record the correct mapped keys);
     
     
     
     
  5. Its all done: the first track will act has an input for the second track (playing instead of you) and the second track will receive and record the keys remapped.
     Just press the record button (TIP: increase the bpm so that it records instantly).
     
  
  Result example (note how the second track has the keys remapped to higher values):
  
  
  
  Resources:
  
  • Addictive Drums & GM MIDI files