How do I record system sound?

Allow microphone access in security settings

Check that you have allowed microphone for the Terminal application in Security & Privacy settings.

Install Blackhole 16ch

Install Blackhole, a virtual audio cable to pass system sound as a microphone.

If you have brew installed, you can just type the following command to Terminal.

brew install blackhole-16c

Add Multi-Output Device and set Blackhole as input

On your desktop type command-space to launch Spotlight and type in midi and press enter to launch Auto MIDI Setup.

In Auto MIDI Setup, click on the bottom left corner + icon and add a new Multi-Output Device. In the list of devices, check Blackhole 16ch and also check your speakers or headphone.

Type command-space to launch Spotlight again and type in sound to launch Sound Settings.

On the Output tab, select Multi-Output Device and on the Input tab select BlackHole 16ch.

Set Blackhole as your audio device

In Game2Text, click on the cogwheel icon to launch the Settings Dialog.

Click on Audio Device and select Blackhole 16ch.

Notes

On Mac OS, automatic recording is disabled when you launch Game2Text but can be re-enabled afterwards.