Sinisterly

Well damn it, I've been passed)
Unlike the other person, I'm naming an online YouTube to MP3 converter.
All you need is a direct link to the video and the website.

Website : ytmp3.cc

Warning: when you click for the first time of your session on the Download button, an ad tab will pop up. Nothing dangerous seems to be appearing, so I simply close it and press Download again.

Works for almost all videos. Description and instructions are written on the website.

Tested on a random video clip, and It works perfectly.

Very stable and responsive.

Yea, this is pretty much how I get all of my music. There are various other yt-2-mp3 converters out there, too.

There is a command line utility called youtube-dl that lets you download plenty of youtube videos, along with tags to convert it to mp3.
sudo apt-get install youtube-dl to install on Linux.
If you don't have Linux, just download it and double click the .exe file. Its what I use