There already had add-on and program to convert YouTube videos to mp3, now I want to introduce an online application to do that, using it, you don't need to download any programs or install other add-ons. This free app is called MP3 Grabber. When you decide to convert which YouTube video to mp3, no need to play it, just copy its link address and paste it into the convert bar on MP3 Grabber. Ok, I told you what I know, hope this helps.