Make sure these are the only PORTS selected in that column (very important). This will allow each of these PORTS to act as inputs to MIDI Tracks you create in Cubase. Go to DEVICES > DEVICE SETUP > MIDI > MIDI PORT SETUP > In the column labeled 'In All MIDI Inputs' place a mark next to the MX's PORT 1 and PORT 3. The computer will identify your MX49 as 'Yamaha MX49/MX61-1' (Port 1), and it will identify your external MIDI keyboard as 'Yamaha MX49/MX61-3' (Port 3).
That means you can use the external MIDI keyboard in the DAW software. it can also act as a MIDI interface for your external keyboard.
Let's say I want to plug a MIDI keyboard in to the MX49 via the MIDI cable Can I still use the USB's audio connection? Like if I want to play sounds from the computer through the MX49's line out?If you want to use the MX49 as your audio interface, this means you connect it to a computer via the USB 'To Host' port.