My friend tipped me off to a neato way to get music off YouTube using terminal.
Yay!
It's called youtube-dl and the GitHub README is a good read (if you're odd like me and get your kicks browsing GitHub).
I've been using this for a while, but I've uninstalled it so I can walk you through the process in a realistic way, from start to finish. I'm on Ubuntu.
1.) Open terminal
2.) sudo apt-get install youtube-dl
3.) sudo apt-get install python-pip
4.) Now, verify pip with pip -v
5.) Now, it's time to upgrade pip with pip install --upgrade pip
6.) Now, you'll need the ffmpeg library (codecs!) but that's easy, just sudo apt-get install mplayer
7.) Now you can download from YouTube at any time! All you will need is terminal and the URL of the YouTube video you want. And remember that to paste into terminal, simply use Ctrl + Shift + V
Try it out!
youtube-dl --extract-audio --audio-format mp3 https://www.youtube.com/watch?v=Zl_GlPquElI