M-300: Can the USB Function as an Audio Interface to Pass Audio To a Computer?
The USB function of the M-300 is to remotely control the console using the RCS software (Remote Control Software) from a computer.
The M-300 USB connection doesn't have audio interface functionality and can't pass audio to/from a computer. A multi-input audio interface would be needed to connect the eight analog outputs of the M-300 to eight analog inputs of the audio interface. Here's an example:
https://www.roland.com/us/products/octa-capture/
Remotely Controlling the M-300 from a Computer:
To control the M-300 from a computer, the M-300 driver and the M-300 RCS software will need to be installed. These can be downloaded here:
https://proav.roland.com/global/products/m-300/downloads/