It is possible to assign two separate MIDI devices to a single keyboard window in RMS Keyboards. This is useful for when you want to incorporate a standalone USB footswitch controller for patch changes, or a separate USB MIDI expression pedal for volume control, or both. Here's how to setup multi-device control on a single keyboard window:

• Launch RMS Keyboards

• Click Tools > Setup Wizard

• On the left-hand column (the detected MIDI devices), click and drag the box representing your standalone USB MIDI device to the box representing your MIDI Keyboard. By clicking and dragging, a line will connect the two boxes.

• Now click and drag from the box representing your MIDI keyboard to the appropriate box on the right column representing the keyboard window to control.
  

• Click "next" and complete the additional steps in the setup wizard.

• Now both the standalone USB device and MIDI Keyboard will both send MIDI data to the designated keyboard window. Expression (CC11) and Volume (CC7) data will control the volume slider. To setup a footswitch so that it changes patches, see our guide located here.