this guide will explain how to set up CMK to work with Reaper.

Requirements

Step 1: Download and install LoopMidi

This guide assumes you already have Reaper installed. Download Loop Midi from the above link and install it. You'll have to check the check box saying I accept the license agreement. I would also make sure the auto start with windows check box is checked. On the end dialog, hit the launch button.

Step 2: Add a port

The next thing we will be doing is adding a port for Reaper and CMK to connect with. We do this by going to the loop midi window that just opened.
There will be a tab control, an edit box, and a few buttons. We mainly want the edit box and the button labeled + (Plus). The edit box contains a default name for the port, Loop MIDI port. You can change this to something like CMK if you'd like to personalize it, but changing the name is not required. After this, you can press the plus button to add the port.

Step 3: Open up reaper and enable the port as an input port

Open up reaper, and press control P to open up the preferences. Go to the audio item in the tree view, and expand it. Next, go down to MIDI devices.
Once there, tab past the OK and cancel buttons. You will see two lists with an Add joystick midi button in between them. You want the first list.
Find your newly created ports in this list. Press either the applications key or right click it with your screen reader. Shift F10 will not work.
Select the configure option. Check both of the check boxes and hit OK, followed by OK to save the preferences.

Step 4: Play away!

Your port is now set. You can now open CMK, select the port, and either press enter or f11 to open the keyboard. Insert a MIDI instrument in reaper and play it with CMK's keyboard!