Some of our Discord channels are push to talk, and some are voice activated, but in the general settings of Discord you have to choose either push to talk or voice activation - unless you setup a hotkey to switch automatically! To do this, go into Discord, Settings (gear in bottom left of window). Then select Keybinds - Add a Keybind. This will add an 'Action' and Keybind window in your list. Under 'Action', select 'Toggle VAD', then set the keybind you want to use. I am using ALT-V.

This will now allow you to push your keybind to switch between push to talk or voice activation.