The USB connection between the MX61 and the computer is digital (both MIDI and Audio) travel from the MX to the computer via the USB cable. Both signals are digital and are inaudible to humans. You will be using the MIDI signal, but not the digital audio... by selecting the UR28M as your audio interface, it will take analog audio in from the MX and convert it to digital for the computer.

You can't hear MIDI (it's just coded messages that represent a musical performance), you can't hear digital audio it's just zeroes and ones), you need to connect the Main L&R Outputs of the MX61 to your audio interface.

The analog signal path should not be confusing for you, novice or not. Connect the L&R Outputs on the back of the MX61 to two channels of your UR28M with regular signal cables and connect the L&R output of the UR28M to your sound system.

In order for you to "hear MIDI" (meaning: in order for you to hear the data that starts out as MIDI messages) you will need to create a MIDI Track in CUBASE (DAW), and echo that data back to the MX61 tone generator, which decodes the MIDI messages and outputs audio... which travels through your signal cables going to the UR28M and finally to your speakers.

In order for you to "hear digital audio" that is recorded on the computer, you will need to Output the audio from the computer via USB to your audio interface, it does the D/A conversions and feeds your speakers.

Thank you for your reply.
I think I've been a bit confused when the MX61 claims that midi AND audio are transmitted via usb. I was hoping to completely avoid having to connect L&R audio out cables to the inputs of the UR28M.
Can I ask then, what does it mean when it says that audio is transmitted to the computer via usb? At the moment it just seems to be using usb for midi data.

MIDI and Audio are transmitted via USB, it no claim, it’s a fact. What you were mistaken about was the fact that you cannot hear digital signals. The digital signals whether MIDI or audio must be converted to analog signal. That is the role of the MX as MIDI interface, that is the role of the MX when tasked with being your Audio Interface.

In any case, your selected audio interface has the responsibility to convert analog audio to digital and send it to the computer, and to take digital audio from the computer and convert it to analog.

You cannot avoid connecting the analog audio Outputs to your sound system... it is the way you can hear it.

Can I ask then, what does it mean when it says that audio is transmitted to the computer via usb? At the moment it just seems to be using usb for midi data?

Okay... let’s remove the UR2M from your setup for a minute. Say all you had was an MX, a USB cable, a computer, and two signal cables that connect your MX to your monitor speakers.

In this scenario, the MX is both your Midi and Audio Interface. It sends MIDI data to the computer. It sends stereo audio digitally to the computer. It receives digital audio from the computer and it converts it to analog and sends it to the speakers.
The MX is your Audio Interface.

When you add a UR28M you have now, two potential audio interfaces, but you must choose just one device to act as your audio in/out device. The primary audio interface is the ONE you connect to your speakers. Only one of them can connect to your speakers... so like a mixer ...all audio sources need to connect to it. From this one audio device you can route digital audio to the computer, and analog audio,to your speakers.

In your setup with the UR28M you could not record the digital audio sent by the MX thru USB because you’re going to select the UR28M as the ONE audio device. You’ll have no direct path for the MX analog signal to get to your speakers... so you would not be able to hear yourself. The analog connection between the MX and your UR28M is for monitoring purposes, you will be sending the audio directly to the speakers... as well as it sending digital audio onto the computer.