How to Sell Youtube to mp3 to a Skeptic
https://golf-wiki.win/index.php?title=Mp3_convert_from_youtube:_It's_Not_as_Difficult_as_You_Think
The finest gamer for the task is the VLC gamer which is available for both Windows and Mac. So next time you hear somebody trying to download YouTube videos as MP4 files you will understand what to inform them.