This section gives you step by step instructions on how to play audio in mono in macOS 12 Monterey, with pictures of the screens to help.
1. Click the Apple icon in the top left corner of the screen and choose System Preferences from the menu.
2. In the System Preferences window, click Accessibility.
3. In the sidebar, click Audio.
4. Tick the checkbox for Play stereo audio as mono.
5. When you are happy with your settings, close System Preferences by clicking the Close button (red circle) in the top-left corner of the window or using the Cmd + W keyboard shortcut.
Note: If this does not work it could be because your computer settings are managed by someone else (an IT department or administrator for example). If so, you will need to contact them to access these settings or for help.