This problem is very easily solved. you honestly don't have to save the video but if you want to read part 1, if you dont want to download the video, skip to part 2.
part 1
first go google "youtube video saver" find a downloader that works through your internet browswer (like tubesaver) or get a firefox plugin that saves them. save it as a .flv (flash video).
part 2 {if you have 'audacity' skip to part 3}
go get the audio mixing program called "audacity". search for it on google.com or go to audacity.sourceforge.net and download it, install it. or if you prefer not to install it go to portableapps.com (a very useful website for getting programs that run on flashdrives without the need of installation), download it, and extract it.
part 3
Run audacity. look for a drop down menu. click the menu, it will drop down and have 2 options. one is "microphone" and the other is "stereo mixer". make sure stereo mixer is selected. make sure no other audio is playing. click the button to record audio and then start playing your video. if you did it right then sound should be recording onto your mixing board for the sound file.
part 4 - yar har, you're a pirate
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