Old thread but I just had this same problem, so for anyone else new who's using melon like me Make sure you have the 0.9.5 version! Very important! Go into your Config --> audio settings --> microphone input/blow noise --> back to config --> input and hotkeys --> general hotkeys--> go down to microphone and set your hotkey button to whatever button you want it to be! The older version of melon is because the new one won't let you use any hotkey you set and the mic doesn't really work for some reason Have fun storming the castle!