AudioThief is a very fast, clean and simple mp3 extractor from YouTube video and it will convert your files in a matter of seconds.
It’s all quite simple: just grab the link of the video you want to convert, paste it and hit the “Convert” button.
Once the conversion is done, you will be able to download your mp3 and even trim it or add some extra tags to it.
This little mp3 thief come with a Firefox and a Chrome extension which will do work for you.
That’s about it. Enjoy it!