I'm a novice looking for help. I want to use midi output from a PA system amplifier as audio input to PC for use in Webex video conferencing. I bought a usb midi interface (Roland UM-ONE) but can't work how to use this as an audio input on my PC. Is there software that can take the midi signal in real time and use it as a "microphone" for video conferencing software? Any advice welcomed.
That won't work. A MIDI output doesn't carry audio. It's used to send control signals between musical instruments ("play note C") and other stage equipment.
What you need is a line-level audio output from the PA system.