I'm not sure I understand. The UX2 does not handle midi, so you can't connect your keyboard to the UX2 as a midi device.

You can use the UX2 as your soundcard and connect your keyboard to your computer/DAW (not to the UX2) for midi purposes as long as you have the required midi interface to your computer.

CrispyGuitar wrote:

 

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Couldn't I connect the keyboards midi output to my computer through USB .

How exactly are you making this connection? Your keyboard has a midi output jack (which is not a usb jack) - you need something to receive the midi data and communicate with Reaper. That something is called a midi interface. It is typically a seperate physical device that has a midi input to receive the data from your keyboard, and a usb output to connect with your computer and handle the midi communications with Reaper. So yes, if you have the required midi interface Reaper will happily communicate with your UX2 for audio and with your midi interface (and hence your keyboard) for midi data.