There is a few different easy to use programs for youtube, you could easily get your hands on by just googling.
This is a link to a site that you can plug in a video URL and download the mp3 directly.
I use youtube music downloader for the most part.. its a program I had downloaded.. need the "full" version to download a complete video. Can download standard, hq, HD 720p, HD 1080p, as well as give you pretty well every option to change the audio bit rate and lots of other good stuff.
I am not SWIM. SWIM is a fictitious character that likes to preform extractions out in space where it is legal to do so. Any and all posts by this user are fictional and are there for entertainment purposes only.